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	$72.92	5.539%	$76.959	$76.96	$76.95	$77.00
Purchase #2	$67.89	7.253%	$72.8141	$72.81	$72.80	$72.80
Purchase #3	$235.65	10.272%	$259.856	$259.86	$259.85	$259.90
Purchase #4	$165.89	11.861%	$185.5662	$185.57	$185.55	$185.60
Purchase #5	$155.55	6.220%	$165.2252	$165.23	$165.25	$165.20
Purchase #6	$181.81	12.224%	$204.0345	$204.03	$204.05	$204.00
Purchase #7	$246.95	4.306%	$257.5837	$257.58	$257.60	$257.60
7 purchase totals =	$1,126.66		$1,222.0387	$1,222.04	$1,222.05	$1,222.10