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	$142.99	5.864%	$151.3749	$151.37	$151.35	$151.40
Purchase #2	$35.28	7.339%	$37.8692	$37.87	$37.85	$37.90
Purchase #3	$96.65	11.113%	$107.3907	$107.39	$107.40	$107.40
Purchase #4	$247.53	6.435%	$263.4586	$263.46	$263.45	$263.50
Purchase #5	$57.61	4.192%	$60.025	$60.03	$60.05	$60.00
Purchase #6	$81.33	13.385%	$92.216	$92.22	$92.20	$92.20
Purchase #7	$51.32	5.622%	$54.2052	$54.21	$54.20	$54.20
7 purchase totals =	$712.71		$766.5396	$766.55	$766.50	$766.60