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	$17.28	9.661%	$18.9494	$18.95	$18.95	$18.90
Purchase #2	$40.36	6.526%	$42.9939	$42.99	$43.00	$43.00
Purchase #3	$145.29	9.561%	$159.1812	$159.18	$159.20	$159.20
Purchase #4	$126.48	13.318%	$143.3246	$143.32	$143.30	$143.30
Purchase #5	$99.33	7.415%	$106.6953	$106.70	$106.70	$106.70
Purchase #6	$52.34	13.526%	$59.4195	$59.42	$59.40	$59.40
Purchase #7	$18.53	13.642%	$21.0579	$21.06	$21.05	$21.10
7 purchase totals =	$499.61		$551.6218	$551.62	$551.60	$551.60