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	$114.65	7.820%	$123.6156	$123.62	$123.60	$123.60
Purchase #2	$103.69	5.846%	$109.7517	$109.75	$109.75	$109.80
Purchase #3	$196.51	13.603%	$223.2413	$223.24	$223.25	$223.20
Purchase #4	$137.60	10.120%	$151.5251	$151.53	$151.55	$151.50
Purchase #5	$133.79	12.496%	$150.5084	$150.51	$150.50	$150.50
Purchase #6	$70.55	12.458%	$79.3391	$79.34	$79.35	$79.30
Purchase #7	$44.55	5.254%	$46.8907	$46.89	$46.90	$46.90
7 purchase totals =	$801.34		$884.8719	$884.88	$884.90	$884.80