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	$21.33	5.222%	$22.4439	$22.44	$22.45	$22.40
Purchase #2	$160.74	5.219%	$169.129	$169.13	$169.15	$169.10
Purchase #3	$103.61	10.629%	$114.6227	$114.62	$114.60	$114.60
Purchase #4	$53.50	13.764%	$60.8637	$60.86	$60.85	$60.90
Purchase #5	$225.48	13.442%	$255.789	$255.79	$255.80	$255.80
Purchase #6	$209.54	6.582%	$223.3319	$223.33	$223.35	$223.30
Purchase #7	$57.35	11.857%	$64.15	$64.15	$64.15	$64.20
7 purchase totals =	$831.55		$910.3302	$910.32	$910.35	$910.30