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	$101.58	11.769%	$113.535	$113.54	$113.55	$113.50
Purchase #2	$201.91	7.659%	$217.3743	$217.37	$217.35	$217.40
Purchase #3	$198.37	6.199%	$210.667	$210.67	$210.65	$210.70
Purchase #4	$242.45	5.219%	$255.1035	$255.10	$255.10	$255.10
Purchase #5	$81.53	9.863%	$89.5713	$89.57	$89.55	$89.60
Purchase #6	$88.55	4.352%	$92.4037	$92.40	$92.40	$92.40
Purchase #7	$39.80	6.277%	$42.2982	$42.30	$42.30	$42.30
7 purchase totals =	$954.19		$1,020.9530	$1,020.95	$1,020.90	$1,021.00