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	$42.38	9.520%	$46.4146	$46.41	$46.40	$46.40
Purchase #2	$61.30	10.750%	$67.8898	$67.89	$67.90	$67.90
Purchase #3	$99.38	10.606%	$109.9202	$109.92	$109.90	$109.90
Purchase #4	$85.91	3.847%	$89.215	$89.22	$89.20	$89.20
Purchase #5	$13.55	13.133%	$15.3295	$15.33	$15.35	$15.30
Purchase #6	$159.76	6.186%	$169.6428	$169.64	$169.65	$169.60
Purchase #7	$59.67	12.430%	$67.087	$67.09	$67.10	$67.10
7 purchase totals =	$521.95		$565.4989	$565.50	$565.50	$565.40