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	$228.77	13.557%	$259.7843	$259.78	$259.80	$259.80
Purchase #2	$54.84	11.167%	$60.964	$60.96	$60.95	$61.00
Purchase #3	$206.75	6.400%	$219.982	$219.98	$220.00	$220.00
Purchase #4	$191.34	13.383%	$216.947	$216.95	$216.95	$216.90
Purchase #5	$136.53	6.539%	$145.4577	$145.46	$145.45	$145.50
Purchase #6	$161.42	10.563%	$178.4708	$178.47	$178.45	$178.50
Purchase #7	$56.95	8.487%	$61.7833	$61.78	$61.80	$61.80
7 purchase totals =	$1,036.60		$1,143.3891	$1,143.38	$1,143.40	$1,143.50