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	$196.42	13.854%	$223.632	$223.63	$223.65	$223.60
Purchase #2	$149.85	3.718%	$155.4214	$155.42	$155.40	$155.40
Purchase #3	$54.67	3.700%	$56.6928	$56.69	$56.70	$56.70
Purchase #4	$223.61	4.793%	$234.3276	$234.33	$234.35	$234.30
Purchase #5	$209.65	12.533%	$235.9254	$235.93	$235.95	$235.90
Purchase #6	$96.89	7.630%	$104.2827	$104.28	$104.30	$104.30
Purchase #7	$59.76	7.243%	$64.0884	$64.09	$64.10	$64.10
7 purchase totals =	$990.85		$1,074.3703	$1,074.37	$1,074.45	$1,074.30