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	$241.78	9.560%	$264.8942	$264.89	$264.90	$264.90
Purchase #2	$81.71	10.347%	$90.1645	$90.16	$90.15	$90.20
Purchase #3	$83.80	7.109%	$89.7573	$89.76	$89.75	$89.80
Purchase #4	$153.68	12.424%	$172.7732	$172.77	$172.75	$172.80
Purchase #5	$91.89	13.742%	$104.5175	$104.52	$104.50	$104.50
Purchase #6	$188.41	7.688%	$202.895	$202.90	$202.90	$202.90
Purchase #7	$154.83	12.180%	$173.6883	$173.69	$173.70	$173.70
7 purchase totals =	$996.10		$1,098.6900	$1,098.69	$1,098.65	$1,098.80