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	$131.33	13.225%	$148.6984	$148.70	$148.70	$148.70
Purchase #2	$191.51	11.873%	$214.248	$214.25	$214.25	$214.20
Purchase #3	$61.31	12.738%	$69.1197	$69.12	$69.10	$69.10
Purchase #4	$147.60	13.358%	$167.3164	$167.32	$167.30	$167.30
Purchase #5	$162.95	6.498%	$173.5385	$173.54	$173.55	$173.50
Purchase #6	$54.92	11.713%	$61.3528	$61.35	$61.35	$61.40
Purchase #7	$139.92	6.418%	$148.9001	$148.90	$148.90	$148.90
7 purchase totals =	$889.54		$983.1739	$983.18	$983.15	$983.10