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	$105.53	11.871%	$118.0575	$118.06	$118.05	$118.10
Purchase #2	$108.60	13.747%	$123.5292	$123.53	$123.55	$123.50
Purchase #3	$99.89	13.516%	$113.3911	$113.39	$113.40	$113.40
Purchase #4	$112.65	9.453%	$123.2988	$123.30	$123.30	$123.30
Purchase #5	$233.59	4.231%	$243.4732	$243.47	$243.45	$243.50
Purchase #6	$105.43	12.747%	$118.8692	$118.87	$118.85	$118.90
Purchase #7	$120.66	4.194%	$125.7205	$125.72	$125.70	$125.70
7 purchase totals =	$886.35		$966.3395	$966.34	$966.30	$966.40