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	$184.93	4.696%	$193.6143	$193.61	$193.60	$193.60
Purchase #2	$242.45	5.487%	$255.7532	$255.75	$255.75	$255.80
Purchase #3	$151.89	5.241%	$159.8506	$159.85	$159.85	$159.90
Purchase #4	$234.91	12.124%	$263.3905	$263.39	$263.40	$263.40
Purchase #5	$51.59	11.512%	$57.529	$57.53	$57.55	$57.50
Purchase #6	$53.79	10.165%	$59.2578	$59.26	$59.25	$59.30
Purchase #7	$54.46	12.465%	$61.2484	$61.25	$61.25	$61.20
7 purchase totals =	$974.02		$1,050.6438	$1,050.64	$1,050.65	$1,050.70