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	$48.75	9.289%	$53.2784	$53.28	$53.30	$53.30
Purchase #2	$228.88	10.636%	$253.2237	$253.22	$253.20	$253.20
Purchase #3	$156.98	10.400%	$173.3059	$173.31	$173.30	$173.30
Purchase #4	$170.98	13.580%	$194.1991	$194.20	$194.20	$194.20
Purchase #5	$43.69	6.521%	$46.539	$46.54	$46.55	$46.50
Purchase #6	$162.54	13.485%	$184.4585	$184.46	$184.45	$184.50
Purchase #7	$154.56	3.461%	$159.9093	$159.91	$159.90	$159.90
7 purchase totals =	$966.38		$1,064.9139	$1,064.92	$1,064.90	$1,064.90