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	$154.84	6.705%	$165.222	$165.22	$165.20	$165.20
Purchase #2	$63.49	6.775%	$67.7914	$67.79	$67.80	$67.80
Purchase #3	$64.79	4.145%	$67.4755	$67.48	$67.50	$67.50
Purchase #4	$101.38	12.352%	$113.9025	$113.90	$113.90	$113.90
Purchase #5	$98.96	6.512%	$105.4043	$105.40	$105.40	$105.40
Purchase #6	$129.78	13.382%	$147.1472	$147.15	$147.15	$147.10
Purchase #7	$127.62	9.279%	$139.4619	$139.46	$139.45	$139.50
7 purchase totals =	$740.86		$806.4048	$806.40	$806.40	$806.40