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	$156.76	5.567%	$165.4868	$165.49	$165.50	$165.50
Purchase #2	$85.59	8.261%	$92.6606	$92.66	$92.65	$92.70
Purchase #3	$133.74	9.801%	$146.8479	$146.85	$146.85	$146.80
Purchase #4	$153.50	9.689%	$168.3726	$168.37	$168.35	$168.40
Purchase #5	$85.67	8.139%	$92.6427	$92.64	$92.65	$92.60
Purchase #6	$250.42	3.425%	$258.9969	$259.00	$259.00	$259.00
Purchase #7	$212.91	11.453%	$237.2946	$237.29	$237.30	$237.30
7 purchase totals =	$1,078.59		$1,162.3021	$1,162.30	$1,162.30	$1,162.30