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	$151.57	5.150%	$159.3759	$159.38	$159.40	$159.40
Purchase #2	$59.26	13.791%	$67.4325	$67.43	$67.45	$67.40
Purchase #3	$118.72	4.139%	$123.6338	$123.63	$123.65	$123.60
Purchase #4	$193.54	3.592%	$200.492	$200.49	$200.50	$200.50
Purchase #5	$117.66	12.294%	$132.1251	$132.13	$132.15	$132.10
Purchase #6	$194.68	5.164%	$204.7333	$204.73	$204.75	$204.70
Purchase #7	$189.62	7.826%	$204.4597	$204.46	$204.45	$204.50
7 purchase totals =	$1,025.05		$1,092.2523	$1,092.25	$1,092.35	$1,092.20