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	$135.65	11.728%	$151.559	$151.56	$151.55	$151.60
Purchase #2	$113.54	3.514%	$117.5298	$117.53	$117.55	$117.50
Purchase #3	$172.65	6.247%	$183.4354	$183.44	$183.45	$183.40
Purchase #4	$216.94	5.860%	$229.6527	$229.65	$229.65	$229.70
Purchase #5	$198.40	12.307%	$222.8171	$222.82	$222.80	$222.80
Purchase #6	$95.47	10.146%	$105.1564	$105.16	$105.15	$105.20
Purchase #7	$43.90	10.139%	$48.351	$48.35	$48.35	$48.40
7 purchase totals =	$976.55		$1,058.5014	$1,058.51	$1,058.50	$1,058.60