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	$103.90	8.543%	$112.7762	$112.78	$112.80	$112.80
Purchase #2	$76.45	11.852%	$85.5109	$85.51	$85.50	$85.50
Purchase #3	$48.56	13.122%	$54.932	$54.93	$54.95	$54.90
Purchase #4	$10.41	13.235%	$11.7878	$11.79	$11.80	$11.80
Purchase #5	$16.54	12.140%	$18.548	$18.55	$18.55	$18.50
Purchase #6	$39.64	6.474%	$42.2063	$42.21	$42.20	$42.20
Purchase #7	$128.70	3.618%	$133.3564	$133.36	$133.35	$133.40
7 purchase totals =	$424.20		$459.1176	$459.13	$459.15	$459.10