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	$159.39	6.523%	$169.787	$169.79	$169.80	$169.80
Purchase #2	$177.27	8.434%	$192.221	$192.22	$192.20	$192.20
Purchase #3	$148.79	12.436%	$167.2935	$167.29	$167.30	$167.30
Purchase #4	$187.79	4.527%	$196.2913	$196.29	$196.30	$196.30
Purchase #5	$193.95	11.727%	$216.6945	$216.69	$216.70	$216.70
Purchase #6	$33.63	4.611%	$35.1807	$35.18	$35.20	$35.20
Purchase #7	$193.27	13.494%	$219.3499	$219.35	$219.35	$219.30
7 purchase totals =	$1,094.09		$1,196.8179	$1,196.81	$1,196.85	$1,196.80