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	$236.50	7.570%	$254.4031	$254.40	$254.40	$254.40
Purchase #2	$175.31	5.670%	$185.2501	$185.25	$185.25	$185.30
Purchase #3	$47.36	3.270%	$48.9087	$48.91	$48.90	$48.90
Purchase #4	$212.62	5.308%	$223.9059	$223.91	$223.90	$223.90
Purchase #5	$191.91	6.773%	$204.9081	$204.91	$204.90	$204.90
Purchase #6	$175.88	9.480%	$192.5534	$192.55	$192.55	$192.60
Purchase #7	$57.48	13.485%	$65.2312	$65.23	$65.25	$65.20
7 purchase totals =	$1,097.06		$1,175.1605	$1,175.16	$1,175.15	$1,175.20