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	$175.90	8.203%	$190.3291	$190.33	$190.35	$190.30
Purchase #2	$86.88	12.685%	$97.9007	$97.90	$97.90	$97.90
Purchase #3	$179.78	6.491%	$191.4495	$191.45	$191.45	$191.40
Purchase #4	$173.50	4.580%	$181.4463	$181.45	$181.45	$181.40
Purchase #5	$237.55	12.846%	$268.0657	$268.07	$268.05	$268.10
Purchase #6	$238.84	7.584%	$256.9536	$256.95	$256.95	$257.00
Purchase #7	$221.84	9.715%	$243.3918	$243.39	$243.40	$243.40
7 purchase totals =	$1,314.29		$1,429.5367	$1,429.54	$1,429.55	$1,429.50