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	$134.82	7.638%	$145.1176	$145.12	$145.10	$145.10
Purchase #2	$131.72	7.501%	$141.6003	$141.60	$141.60	$141.60
Purchase #3	$120.36	13.511%	$136.6218	$136.62	$136.60	$136.60
Purchase #4	$178.99	12.200%	$200.8268	$200.83	$200.85	$200.80
Purchase #5	$166.69	4.814%	$174.7145	$174.71	$174.70	$174.70
Purchase #6	$12.74	9.148%	$13.9055	$13.91	$13.90	$13.90
Purchase #7	$190.76	6.676%	$203.4951	$203.50	$203.50	$203.50
7 purchase totals =	$936.08		$1,016.2816	$1,016.29	$1,016.25	$1,016.20