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	$208.75	11.851%	$233.489	$233.49	$233.50	$233.50
Purchase #2	$202.26	4.676%	$211.7177	$211.72	$211.70	$211.70
Purchase #3	$141.30	5.122%	$148.5374	$148.54	$148.55	$148.50
Purchase #4	$141.99	11.476%	$158.2848	$158.28	$158.30	$158.30
Purchase #5	$202.37	3.758%	$209.9751	$209.98	$210.00	$210.00
Purchase #6	$194.64	8.467%	$211.1202	$211.12	$211.10	$211.10
Purchase #7	$75.42	9.347%	$82.4695	$82.47	$82.45	$82.50
7 purchase totals =	$1,166.73		$1,255.5937	$1,255.60	$1,255.60	$1,255.60