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	$54.45	12.591%	$61.3058	$61.31	$61.30	$61.30
Purchase #2	$218.67	11.279%	$243.3338	$243.33	$243.35	$243.30
Purchase #3	$60.65	8.601%	$65.8665	$65.87	$65.85	$65.90
Purchase #4	$136.53	10.697%	$151.1346	$151.13	$151.15	$151.10
Purchase #5	$139.89	6.394%	$148.8346	$148.83	$148.85	$148.80
Purchase #6	$95.40	12.411%	$107.2401	$107.24	$107.25	$107.20
Purchase #7	$224.97	8.725%	$244.5986	$244.60	$244.60	$244.60
7 purchase totals =	$930.56		$1,022.3140	$1,022.31	$1,022.35	$1,022.20