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	$36.25	5.727%	$38.326	$38.33	$38.35	$38.30
Purchase #2	$149.37	6.805%	$159.5346	$159.53	$159.55	$159.50
Purchase #3	$91.76	4.641%	$96.0186	$96.02	$96.00	$96.00
Purchase #4	$177.69	6.461%	$189.1706	$189.17	$189.15	$189.20
Purchase #5	$91.63	8.682%	$99.5853	$99.59	$99.60	$99.60
Purchase #6	$180.83	12.718%	$203.828	$203.83	$203.85	$203.80
Purchase #7	$208.48	7.419%	$223.9471	$223.95	$223.95	$223.90
7 purchase totals =	$936.01		$1,010.4102	$1,010.42	$1,010.45	$1,010.30