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	$154.41	11.682%	$172.4482	$172.45	$172.45	$172.40
Purchase #2	$175.37	6.768%	$187.239	$187.24	$187.25	$187.20
Purchase #3	$98.28	9.626%	$107.7404	$107.74	$107.75	$107.70
Purchase #4	$171.71	5.311%	$180.8295	$180.83	$180.85	$180.80
Purchase #5	$99.91	5.522%	$105.427	$105.43	$105.45	$105.40
Purchase #6	$177.33	10.530%	$196.0028	$196.00	$196.00	$196.00
Purchase #7	$179.88	12.231%	$201.8811	$201.88	$201.90	$201.90
7 purchase totals =	$1,056.89		$1,151.5680	$1,151.57	$1,151.65	$1,151.40