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	$141.38	10.805%	$156.6561	$156.66	$156.65	$156.70
Purchase #2	$91.75	5.339%	$96.6485	$96.65	$96.65	$96.60
Purchase #3	$78.52	5.517%	$82.8519	$82.85	$82.85	$82.90
Purchase #4	$222.53	3.289%	$229.849	$229.85	$229.85	$229.80
Purchase #5	$168.57	7.210%	$180.7239	$180.72	$180.70	$180.70
Purchase #6	$46.95	7.505%	$50.4736	$50.47	$50.45	$50.50
Purchase #7	$60.48	4.344%	$63.1073	$63.11	$63.10	$63.10
7 purchase totals =	$810.18		$860.3103	$860.31	$860.25	$860.30