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	$172.84	5.658%	$182.6193	$182.62	$182.60	$182.60
Purchase #2	$43.64	7.262%	$46.8091	$46.81	$46.80	$46.80
Purchase #3	$205.91	8.287%	$222.9738	$222.97	$222.95	$223.00
Purchase #4	$172.47	7.272%	$185.012	$185.01	$185.00	$185.00
Purchase #5	$116.66	12.614%	$131.3755	$131.38	$131.40	$131.40
Purchase #6	$212.62	5.292%	$223.8719	$223.87	$223.85	$223.90
Purchase #7	$51.56	3.700%	$53.4677	$53.47	$53.45	$53.50
7 purchase totals =	$975.70		$1,046.1293	$1,046.13	$1,046.05	$1,046.20