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	$53.78	4.354%	$56.1216	$56.12	$56.10	$56.10
Purchase #2	$70.34	3.318%	$72.6739	$72.67	$72.65	$72.70
Purchase #3	$200.54	11.146%	$222.8922	$222.89	$222.90	$222.90
Purchase #4	$64.71	4.103%	$67.3651	$67.37	$67.35	$67.40
Purchase #5	$138.60	10.681%	$153.4039	$153.40	$153.40	$153.40
Purchase #6	$68.45	5.741%	$72.3797	$72.38	$72.40	$72.40
Purchase #7	$189.46	10.574%	$209.4935	$209.49	$209.50	$209.50
7 purchase totals =	$785.88		$854.3299	$854.32	$854.30	$854.40