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	$229.32	9.524%	$251.1604	$251.16	$251.15	$251.20
Purchase #2	$172.91	13.455%	$196.175	$196.18	$196.20	$196.20
Purchase #3	$135.71	10.357%	$149.7655	$149.77	$149.75	$149.80
Purchase #4	$235.50	13.275%	$266.7626	$266.76	$266.75	$266.80
Purchase #5	$128.83	10.535%	$142.4022	$142.40	$142.40	$142.40
Purchase #6	$109.81	6.116%	$116.526	$116.53	$116.55	$116.50
Purchase #7	$136.39	4.740%	$142.8549	$142.85	$142.85	$142.90
7 purchase totals =	$1,148.47		$1,265.6466	$1,265.65	$1,265.65	$1,265.80