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	$88.50	11.801%	$98.9439	$98.94	$98.95	$98.90
Purchase #2	$59.48	7.135%	$63.7239	$63.72	$63.70	$63.70
Purchase #3	$165.59	7.680%	$178.3073	$178.31	$178.30	$178.30
Purchase #4	$160.43	11.711%	$179.218	$179.22	$179.20	$179.20
Purchase #5	$151.91	10.283%	$167.5309	$167.53	$167.55	$167.50
Purchase #6	$245.28	12.756%	$276.5679	$276.57	$276.55	$276.60
Purchase #7	$37.73	12.326%	$42.3806	$42.38	$42.40	$42.40
7 purchase totals =	$908.92		$1,006.6725	$1,006.67	$1,006.65	$1,006.60