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	$154.57	8.370%	$167.5075	$167.51	$167.50	$167.50
Purchase #2	$11.58	6.188%	$12.2966	$12.30	$12.30	$12.30
Purchase #3	$54.29	9.695%	$59.5534	$59.55	$59.55	$59.60
Purchase #4	$87.29	10.539%	$96.4895	$96.49	$96.50	$96.50
Purchase #5	$125.42	6.280%	$133.2964	$133.30	$133.30	$133.30
Purchase #6	$40.88	12.279%	$45.8997	$45.90	$45.90	$45.90
Purchase #7	$236.76	5.352%	$249.4314	$249.43	$249.45	$249.40
7 purchase totals =	$710.79		$764.4745	$764.48	$764.50	$764.50