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	$98.34	11.764%	$109.9087	$109.91	$109.90	$109.90
Purchase #2	$218.61	13.573%	$248.2819	$248.28	$248.30	$248.30
Purchase #3	$76.96	4.821%	$80.6702	$80.67	$80.65	$80.70
Purchase #4	$22.48	9.563%	$24.6298	$24.63	$24.65	$24.60
Purchase #5	$230.50	6.308%	$245.0399	$245.04	$245.05	$245.00
Purchase #6	$168.46	4.162%	$175.4713	$175.47	$175.45	$175.50
Purchase #7	$199.85	5.212%	$210.2662	$210.27	$210.25	$210.30
7 purchase totals =	$1,015.20		$1,094.2680	$1,094.27	$1,094.25	$1,094.30