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	$168.68	6.315%	$179.3321	$179.33	$179.35	$179.30
Purchase #2	$24.89	6.784%	$26.5785	$26.58	$26.60	$26.60
Purchase #3	$192.63	8.738%	$209.462	$209.46	$209.45	$209.50
Purchase #4	$213.90	7.579%	$230.1115	$230.11	$230.10	$230.10
Purchase #5	$125.78	4.834%	$131.8602	$131.86	$131.85	$131.90
Purchase #6	$105.74	5.840%	$111.9152	$111.92	$111.90	$111.90
Purchase #7	$250.76	13.807%	$285.3824	$285.38	$285.40	$285.40
7 purchase totals =	$1,082.38		$1,174.6419	$1,174.64	$1,174.65	$1,174.70