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	$107.96	3.837%	$112.1024	$112.10	$112.10	$112.10
Purchase #2	$144.31	6.324%	$153.4362	$153.44	$153.45	$153.40
Purchase #3	$42.25	10.560%	$46.7116	$46.71	$46.70	$46.70
Purchase #4	$172.54	13.686%	$196.1538	$196.15	$196.15	$196.20
Purchase #5	$31.75	3.222%	$32.773	$32.77	$32.75	$32.80
Purchase #6	$239.93	12.640%	$270.2572	$270.26	$270.25	$270.30
Purchase #7	$219.80	6.406%	$233.8804	$233.88	$233.90	$233.90
7 purchase totals =	$958.54		$1,045.3146	$1,045.31	$1,045.30	$1,045.40