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	$121.63	5.152%	$127.8964	$127.90	$127.90	$127.90
Purchase #2	$106.40	5.499%	$112.2509	$112.25	$112.25	$112.30
Purchase #3	$64.70	7.459%	$69.526	$69.53	$69.55	$69.50
Purchase #4	$36.34	11.136%	$40.3868	$40.39	$40.40	$40.40
Purchase #5	$86.68	11.579%	$96.7167	$96.72	$96.70	$96.70
Purchase #6	$244.38	4.851%	$256.2349	$256.23	$256.25	$256.20
Purchase #7	$109.69	6.380%	$116.6882	$116.69	$116.70	$116.70
7 purchase totals =	$769.82		$819.6999	$819.71	$819.75	$819.70