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	$187.55	6.772%	$200.2509	$200.25	$200.25	$200.30
Purchase #2	$142.80	13.479%	$162.048	$162.05	$162.05	$162.00
Purchase #3	$190.59	5.338%	$200.7637	$200.76	$200.75	$200.80
Purchase #4	$94.41	9.137%	$103.0362	$103.04	$103.05	$103.00
Purchase #5	$66.87	4.805%	$70.0831	$70.08	$70.10	$70.10
Purchase #6	$152.44	10.494%	$168.4371	$168.44	$168.45	$168.40
Purchase #7	$208.93	6.427%	$222.3579	$222.36	$222.35	$222.40
7 purchase totals =	$1,043.59		$1,126.9769	$1,126.98	$1,127.00	$1,127.00