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	$142.73	8.644%	$155.0676	$155.07	$155.05	$155.10
Purchase #2	$168.52	13.364%	$191.041	$191.04	$191.05	$191.00
Purchase #3	$69.62	3.523%	$72.0727	$72.07	$72.05	$72.10
Purchase #4	$32.50	12.250%	$36.4813	$36.48	$36.50	$36.50
Purchase #5	$70.39	11.602%	$78.5566	$78.56	$78.55	$78.60
Purchase #6	$165.88	9.405%	$181.481	$181.48	$181.50	$181.50
Purchase #7	$14.46	6.106%	$15.3429	$15.34	$15.35	$15.30
7 purchase totals =	$664.10		$730.0431	$730.04	$730.05	$730.10