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	$108.50	5.560%	$114.5326	$114.53	$114.55	$114.50
Purchase #2	$183.63	4.162%	$191.2727	$191.27	$191.25	$191.30
Purchase #3	$188.50	4.202%	$196.4208	$196.42	$196.40	$196.40
Purchase #4	$166.25	13.167%	$188.1401	$188.14	$188.15	$188.10
Purchase #5	$19.90	11.418%	$22.1722	$22.17	$22.15	$22.20
Purchase #6	$225.80	5.276%	$237.7132	$237.71	$237.70	$237.70
Purchase #7	$145.89	3.235%	$150.6095	$150.61	$150.60	$150.60
7 purchase totals =	$1,038.47		$1,100.8611	$1,100.85	$1,100.80	$1,100.80