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	$64.56	11.736%	$72.1368	$72.14	$72.15	$72.10
Purchase #2	$213.90	8.612%	$232.3211	$232.32	$232.30	$232.30
Purchase #3	$199.52	5.757%	$211.0064	$211.01	$211.00	$211.00
Purchase #4	$205.39	11.181%	$228.3547	$228.35	$228.35	$228.40
Purchase #5	$55.85	12.597%	$62.8854	$62.89	$62.90	$62.90
Purchase #6	$45.73	10.803%	$50.6702	$50.67	$50.65	$50.70
Purchase #7	$226.71	7.149%	$242.9175	$242.92	$242.90	$242.90
7 purchase totals =	$1,011.66		$1,100.2921	$1,100.30	$1,100.25	$1,100.30