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	$52.38	3.712%	$54.3243	$54.32	$54.30	$54.30
Purchase #2	$243.89	9.721%	$267.5985	$267.60	$267.60	$267.60
Purchase #3	$147.28	13.290%	$166.8535	$166.85	$166.85	$166.90
Purchase #4	$205.28	9.865%	$225.5309	$225.53	$225.55	$225.50
Purchase #5	$34.94	8.269%	$37.8292	$37.83	$37.85	$37.80
Purchase #6	$151.91	11.108%	$168.7842	$168.78	$168.80	$168.80
Purchase #7	$124.46	7.197%	$133.4174	$133.42	$133.40	$133.40
7 purchase totals =	$960.14		$1,054.3380	$1,054.33	$1,054.35	$1,054.30