Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.83	12.771%	$250.1599	$250.16	$250.15	$250.20
Purchase #2	$152.56	13.688%	$173.4424	$173.44	$173.45	$173.40
Purchase #3	$152.36	10.608%	$168.5223	$168.52	$168.50	$168.50
Purchase #4	$152.34	7.772%	$164.1799	$164.18	$164.20	$164.20
Purchase #5	$187.51	13.142%	$212.1526	$212.15	$212.15	$212.20
Purchase #6	$185.80	6.436%	$197.7581	$197.76	$197.75	$197.80
Purchase #7	$96.76	8.542%	$105.0252	$105.03	$105.05	$105.00
7 purchase totals =	$1,149.16		$1,271.2404	$1,271.24	$1,271.25	$1,271.30