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	$196.84	6.162%	$208.9693	$208.97	$208.95	$209.00
Purchase #2	$115.81	7.678%	$124.7019	$124.70	$124.70	$124.70
Purchase #3	$188.83	11.428%	$210.4095	$210.41	$210.40	$210.40
Purchase #4	$47.39	8.200%	$51.276	$51.28	$51.30	$51.30
Purchase #5	$114.35	12.650%	$128.8153	$128.82	$128.80	$128.80
Purchase #6	$239.80	10.496%	$264.9694	$264.97	$264.95	$265.00
Purchase #7	$107.40	3.415%	$111.0677	$111.07	$111.05	$111.10
7 purchase totals =	$1,010.42		$1,100.2091	$1,100.22	$1,100.15	$1,100.30