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	$178.53	8.803%	$194.246	$194.25	$194.25	$194.20
Purchase #2	$140.74	7.407%	$151.1646	$151.16	$151.15	$151.20
Purchase #3	$39.31	4.332%	$41.0129	$41.01	$41.00	$41.00
Purchase #4	$168.78	13.592%	$191.7206	$191.72	$191.70	$191.70
Purchase #5	$216.26	10.326%	$238.591	$238.59	$238.60	$238.60
Purchase #6	$152.53	12.209%	$171.1524	$171.15	$171.15	$171.20
Purchase #7	$196.62	3.694%	$203.8831	$203.88	$203.90	$203.90
7 purchase totals =	$1,092.77		$1,191.7706	$1,191.76	$1,191.75	$1,191.80