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	$162.47	10.411%	$179.3848	$179.38	$179.40	$179.40
Purchase #2	$54.51	5.140%	$57.3118	$57.31	$57.30	$57.30
Purchase #3	$223.76	4.265%	$233.3034	$233.30	$233.30	$233.30
Purchase #4	$7.85	8.367%	$8.5068	$8.51	$8.50	$8.50
Purchase #5	$59.62	9.572%	$65.3268	$65.33	$65.35	$65.30
Purchase #6	$103.60	9.265%	$113.1985	$113.20	$113.20	$113.20
Purchase #7	$161.85	4.670%	$169.4084	$169.41	$169.40	$169.40
7 purchase totals =	$773.66		$826.4405	$826.44	$826.45	$826.40