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	$126.27	12.844%	$142.4881	$142.49	$142.50	$142.50
Purchase #2	$173.49	6.787%	$185.2648	$185.26	$185.25	$185.30
Purchase #3	$98.35	6.323%	$104.5687	$104.57	$104.55	$104.60
Purchase #4	$36.62	3.643%	$37.9541	$37.95	$37.95	$38.00
Purchase #5	$101.38	4.194%	$105.6319	$105.63	$105.65	$105.60
Purchase #6	$234.73	10.530%	$259.4471	$259.45	$259.45	$259.40
Purchase #7	$38.77	10.315%	$42.7691	$42.77	$42.75	$42.80
7 purchase totals =	$809.61		$878.1238	$878.12	$878.10	$878.20