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	$184.79	6.446%	$196.7016	$196.70	$196.70	$196.70
Purchase #2	$40.94	8.396%	$44.3773	$44.38	$44.40	$44.40
Purchase #3	$161.32	10.570%	$178.3715	$178.37	$178.35	$178.40
Purchase #4	$42.57	5.234%	$44.7981	$44.80	$44.80	$44.80
Purchase #5	$86.57	5.167%	$91.0431	$91.04	$91.05	$91.00
Purchase #6	$219.27	11.850%	$245.2535	$245.25	$245.25	$245.30
Purchase #7	$212.86	7.847%	$229.5631	$229.56	$229.55	$229.60
7 purchase totals =	$948.32		$1,030.1082	$1,030.10	$1,030.10	$1,030.20