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	$167.84	4.379%	$175.1897	$175.19	$175.20	$175.20
Purchase #2	$181.27	5.302%	$190.8809	$190.88	$190.90	$190.90
Purchase #3	$121.29	7.524%	$130.4159	$130.42	$130.40	$130.40
Purchase #4	$40.65	11.129%	$45.1739	$45.17	$45.15	$45.20
Purchase #5	$199.52	5.711%	$210.9146	$210.91	$210.90	$210.90
Purchase #6	$49.70	11.818%	$55.5735	$55.57	$55.55	$55.60
Purchase #7	$238.39	7.586%	$256.4743	$256.47	$256.45	$256.50
7 purchase totals =	$998.66		$1,064.6228	$1,064.61	$1,064.55	$1,064.70