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	$75.83	13.594%	$86.1383	$86.14	$86.15	$86.10
Purchase #2	$222.83	13.482%	$252.8719	$252.87	$252.85	$252.90
Purchase #3	$147.71	3.281%	$152.5564	$152.56	$152.55	$152.60
Purchase #4	$45.43	6.417%	$48.3452	$48.35	$48.35	$48.30
Purchase #5	$175.27	5.450%	$184.8222	$184.82	$184.80	$184.80
Purchase #6	$160.31	7.232%	$171.9036	$171.90	$171.90	$171.90
Purchase #7	$198.93	8.771%	$216.3782	$216.38	$216.40	$216.40
7 purchase totals =	$1,026.31		$1,113.0158	$1,113.02	$1,113.00	$1,113.00