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	$191.45	9.472%	$209.5841	$209.58	$209.60	$209.60
Purchase #2	$225.59	12.697%	$254.2332	$254.23	$254.25	$254.20
Purchase #3	$71.93	11.138%	$79.9416	$79.94	$79.95	$79.90
Purchase #4	$164.46	6.629%	$175.3621	$175.36	$175.35	$175.40
Purchase #5	$94.59	5.591%	$99.8785	$99.88	$99.90	$99.90
Purchase #6	$35.55	11.698%	$39.7086	$39.71	$39.70	$39.70
Purchase #7	$158.84	13.213%	$179.8275	$179.83	$179.85	$179.80
7 purchase totals =	$942.41		$1,038.5356	$1,038.53	$1,038.60	$1,038.50