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	$195.79	13.445%	$222.114	$222.11	$222.10	$222.10
Purchase #2	$62.81	6.488%	$66.8851	$66.89	$66.90	$66.90
Purchase #3	$74.31	10.798%	$82.334	$82.33	$82.35	$82.30
Purchase #4	$102.78	12.735%	$115.869	$115.87	$115.85	$115.90
Purchase #5	$38.96	10.409%	$43.0153	$43.02	$43.00	$43.00
Purchase #6	$149.43	5.139%	$157.1092	$157.11	$157.10	$157.10
Purchase #7	$147.72	8.124%	$159.7208	$159.72	$159.70	$159.70
7 purchase totals =	$771.80		$847.0474	$847.05	$847.00	$847.00