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	$156.25	6.117%	$165.8078	$165.81	$165.80	$165.80
Purchase #2	$85.59	6.804%	$91.4135	$91.41	$91.40	$91.40
Purchase #3	$158.54	4.607%	$165.8439	$165.84	$165.85	$165.80
Purchase #4	$43.91	5.230%	$46.2065	$46.21	$46.20	$46.20
Purchase #5	$232.40	3.538%	$240.6223	$240.62	$240.60	$240.60
Purchase #6	$174.59	10.724%	$193.313	$193.31	$193.30	$193.30
Purchase #7	$178.90	7.499%	$192.3157	$192.32	$192.30	$192.30
7 purchase totals =	$1,030.18		$1,095.5227	$1,095.52	$1,095.45	$1,095.40