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	$55.57	11.181%	$61.7833	$61.78	$61.80	$61.80
Purchase #2	$130.68	13.502%	$148.3244	$148.32	$148.30	$148.30
Purchase #3	$143.78	10.494%	$158.8683	$158.87	$158.85	$158.90
Purchase #4	$155.79	7.729%	$167.831	$167.83	$167.85	$167.80
Purchase #5	$178.55	6.849%	$190.7789	$190.78	$190.80	$190.80
Purchase #6	$63.65	7.248%	$68.2634	$68.26	$68.25	$68.30
Purchase #7	$192.93	7.584%	$207.5618	$207.56	$207.55	$207.60
7 purchase totals =	$920.95		$1,003.4111	$1,003.40	$1,003.40	$1,003.50