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	$147.66	12.138%	$165.583	$165.58	$165.60	$165.60
Purchase #2	$112.94	9.439%	$123.6004	$123.60	$123.60	$123.60
Purchase #3	$96.28	11.764%	$107.6064	$107.61	$107.60	$107.60
Purchase #4	$209.40	4.783%	$219.4156	$219.42	$219.40	$219.40
Purchase #5	$74.89	11.760%	$83.6971	$83.70	$83.70	$83.70
Purchase #6	$191.97	11.267%	$213.5993	$213.60	$213.60	$213.60
Purchase #7	$26.61	8.802%	$28.9522	$28.95	$28.95	$29.00
7 purchase totals =	$859.75		$942.4540	$942.46	$942.45	$942.50