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	$189.97	5.293%	$200.0251	$200.03	$200.05	$200.00
Purchase #2	$122.63	4.307%	$127.9117	$127.91	$127.90	$127.90
Purchase #3	$28.95	9.634%	$31.739	$31.74	$31.75	$31.70
Purchase #4	$44.88	12.832%	$50.639	$50.64	$50.65	$50.60
Purchase #5	$248.49	6.700%	$265.1388	$265.14	$265.15	$265.10
Purchase #6	$243.66	8.310%	$263.9081	$263.91	$263.90	$263.90
Purchase #7	$143.54	10.735%	$158.949	$158.95	$158.95	$158.90
7 purchase totals =	$1,022.12		$1,098.3107	$1,098.32	$1,098.35	$1,098.10