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	$89.51	7.390%	$96.1248	$96.12	$96.10	$96.10
Purchase #2	$97.99	11.826%	$109.5783	$109.58	$109.60	$109.60
Purchase #3	$155.33	4.771%	$162.7408	$162.74	$162.75	$162.70
Purchase #4	$64.82	11.677%	$72.389	$72.39	$72.40	$72.40
Purchase #5	$218.65	3.847%	$227.0615	$227.06	$227.05	$227.10
Purchase #6	$128.64	8.215%	$139.2078	$139.21	$139.20	$139.20
Purchase #7	$247.59	13.704%	$281.5197	$281.52	$281.50	$281.50
7 purchase totals =	$1,002.53		$1,088.6219	$1,088.62	$1,088.60	$1,088.60