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	$211.58	8.872%	$230.3514	$230.35	$230.35	$230.40
Purchase #2	$228.91	7.300%	$245.6204	$245.62	$245.60	$245.60
Purchase #3	$165.97	6.784%	$177.2294	$177.23	$177.25	$177.20
Purchase #4	$139.61	7.636%	$150.2706	$150.27	$150.25	$150.30
Purchase #5	$150.32	4.288%	$156.7657	$156.77	$156.75	$156.80
Purchase #6	$19.60	4.600%	$20.5016	$20.50	$20.50	$20.50
Purchase #7	$33.40	11.466%	$37.2296	$37.23	$37.25	$37.20
7 purchase totals =	$949.39		$1,017.9687	$1,017.97	$1,017.95	$1,018.00