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	$131.89	10.748%	$146.0655	$146.07	$146.05	$146.10
Purchase #2	$151.83	6.255%	$161.327	$161.33	$161.35	$161.30
Purchase #3	$196.80	4.501%	$205.658	$205.66	$205.65	$205.70
Purchase #4	$94.89	4.745%	$99.3925	$99.39	$99.40	$99.40
Purchase #5	$102.70	6.244%	$109.1126	$109.11	$109.10	$109.10
Purchase #6	$48.40	11.313%	$53.8755	$53.88	$53.90	$53.90
Purchase #7	$229.75	10.411%	$253.6693	$253.67	$253.65	$253.70
7 purchase totals =	$956.26		$1,029.1004	$1,029.11	$1,029.10	$1,029.20