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	$228.64	4.220%	$238.2886	$238.29	$238.30	$238.30
Purchase #2	$15.82	11.590%	$17.6535	$17.65	$17.65	$17.70
Purchase #3	$85.42	12.706%	$96.2735	$96.27	$96.25	$96.30
Purchase #4	$109.71	7.692%	$118.1489	$118.15	$118.15	$118.10
Purchase #5	$243.44	8.538%	$264.2249	$264.22	$264.20	$264.20
Purchase #6	$216.72	9.743%	$237.835	$237.84	$237.85	$237.80
Purchase #7	$91.71	8.298%	$99.3201	$99.32	$99.30	$99.30
7 purchase totals =	$991.46		$1,071.7445	$1,071.74	$1,071.70	$1,071.70