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	$184.44	3.618%	$191.113	$191.11	$191.10	$191.10
Purchase #2	$148.72	13.275%	$168.4626	$168.46	$168.45	$168.50
Purchase #3	$148.96	11.857%	$166.6222	$166.62	$166.60	$166.60
Purchase #4	$239.89	8.348%	$259.916	$259.92	$259.90	$259.90
Purchase #5	$77.73	13.755%	$88.4218	$88.42	$88.40	$88.40
Purchase #6	$50.75	8.318%	$54.9714	$54.97	$54.95	$55.00
Purchase #7	$108.31	11.213%	$120.4548	$120.45	$120.45	$120.50
7 purchase totals =	$958.80		$1,049.9618	$1,049.95	$1,049.85	$1,050.00