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	$41.57	12.275%	$46.6727	$46.67	$46.65	$46.70
Purchase #2	$81.73	4.477%	$85.3891	$85.39	$85.40	$85.40
Purchase #3	$33.50	5.294%	$35.2735	$35.27	$35.25	$35.30
Purchase #4	$38.72	5.117%	$40.7013	$40.70	$40.70	$40.70
Purchase #5	$39.36	9.660%	$43.1622	$43.16	$43.15	$43.20
Purchase #6	$42.52	10.112%	$46.8196	$46.82	$46.80	$46.80
Purchase #7	$173.78	12.148%	$194.8908	$194.89	$194.90	$194.90
7 purchase totals =	$451.18		$492.9092	$492.90	$492.85	$493.00