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	$40.69	6.171%	$43.201	$43.20	$43.20	$43.20
Purchase #2	$73.61	13.562%	$83.593	$83.59	$83.60	$83.60
Purchase #3	$113.25	4.399%	$118.2319	$118.23	$118.25	$118.20
Purchase #4	$75.45	13.557%	$85.6788	$85.68	$85.70	$85.70
Purchase #5	$30.28	9.231%	$33.0751	$33.08	$33.10	$33.10
Purchase #6	$73.76	13.700%	$83.8651	$83.87	$83.85	$83.90
Purchase #7	$227.64	6.819%	$243.1628	$243.16	$243.15	$243.20
7 purchase totals =	$634.68		$690.8077	$690.81	$690.85	$690.90