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	$175.94	7.761%	$189.5947	$189.59	$189.60	$189.60
Purchase #2	$211.77	13.481%	$240.3187	$240.32	$240.30	$240.30
Purchase #3	$164.28	6.604%	$175.1291	$175.13	$175.15	$175.10
Purchase #4	$156.55	5.865%	$165.7317	$165.73	$165.75	$165.70
Purchase #5	$20.89	6.145%	$22.1737	$22.17	$22.15	$22.20
Purchase #6	$155.92	10.581%	$172.4179	$172.42	$172.40	$172.40
Purchase #7	$51.25	9.870%	$56.3084	$56.31	$56.30	$56.30
7 purchase totals =	$936.60		$1,021.6742	$1,021.67	$1,021.65	$1,021.60