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	$174.82	6.359%	$185.9368	$185.94	$185.95	$185.90
Purchase #2	$17.89	6.666%	$19.0825	$19.08	$19.10	$19.10
Purchase #3	$41.67	7.332%	$44.7252	$44.73	$44.75	$44.70
Purchase #4	$71.77	9.395%	$78.5128	$78.51	$78.50	$78.50
Purchase #5	$225.74	9.644%	$247.5104	$247.51	$247.50	$247.50
Purchase #6	$89.81	11.234%	$99.8993	$99.90	$99.90	$99.90
Purchase #7	$18.34	5.335%	$19.3184	$19.32	$19.30	$19.30
7 purchase totals =	$640.04		$694.9854	$694.99	$695.00	$694.90