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	$98.47	11.841%	$110.1298	$110.13	$110.15	$110.10
Purchase #2	$143.79	13.258%	$162.8537	$162.85	$162.85	$162.90
Purchase #3	$69.63	12.751%	$78.5085	$78.51	$78.50	$78.50
Purchase #4	$17.48	11.825%	$19.547	$19.55	$19.55	$19.50
Purchase #5	$245.52	12.852%	$277.0742	$277.07	$277.05	$277.10
Purchase #6	$42.78	4.774%	$44.8223	$44.82	$44.80	$44.80
Purchase #7	$250.80	11.454%	$279.5266	$279.53	$279.55	$279.50
7 purchase totals =	$868.47		$972.4621	$972.46	$972.45	$972.40