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	$94.73	11.527%	$105.6495	$105.65	$105.65	$105.60
Purchase #2	$83.63	9.145%	$91.278	$91.28	$91.30	$91.30
Purchase #3	$195.89	11.750%	$218.9071	$218.91	$218.90	$218.90
Purchase #4	$124.94	9.161%	$136.3858	$136.39	$136.40	$136.40
Purchase #5	$59.55	5.551%	$62.8556	$62.86	$62.85	$62.90
Purchase #6	$237.64	3.326%	$245.5439	$245.54	$245.55	$245.50
Purchase #7	$98.96	4.203%	$103.1193	$103.12	$103.10	$103.10
7 purchase totals =	$895.34		$963.7392	$963.75	$963.75	$963.70