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	$250.87	5.579%	$264.866	$264.87	$264.85	$264.90
Purchase #2	$166.94	8.152%	$180.5489	$180.55	$180.55	$180.50
Purchase #3	$140.58	10.734%	$155.6699	$155.67	$155.65	$155.70
Purchase #4	$120.46	11.267%	$134.0322	$134.03	$134.05	$134.00
Purchase #5	$241.64	10.519%	$267.0581	$267.06	$267.05	$267.10
Purchase #6	$17.72	6.642%	$18.897	$18.90	$18.90	$18.90
Purchase #7	$124.67	5.445%	$131.4583	$131.46	$131.45	$131.50
7 purchase totals =	$1,062.88		$1,152.5304	$1,152.54	$1,152.50	$1,152.60