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	$59.87	9.202%	$65.3792	$65.38	$65.40	$65.40
Purchase #2	$162.85	5.604%	$171.9761	$171.98	$172.00	$172.00
Purchase #3	$203.38	10.205%	$224.1349	$224.13	$224.15	$224.10
Purchase #4	$143.80	8.526%	$156.0604	$156.06	$156.05	$156.10
Purchase #5	$141.27	7.813%	$152.3074	$152.31	$152.30	$152.30
Purchase #6	$245.59	13.312%	$278.2829	$278.28	$278.30	$278.30
Purchase #7	$214.44	6.272%	$227.8897	$227.89	$227.90	$227.90
7 purchase totals =	$1,171.20		$1,276.0306	$1,276.03	$1,276.10	$1,276.10