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	$98.37	7.273%	$105.5245	$105.52	$105.50	$105.50
Purchase #2	$190.37	13.656%	$216.3669	$216.37	$216.35	$216.40
Purchase #3	$250.61	3.485%	$259.3438	$259.34	$259.35	$259.30
Purchase #4	$72.57	3.583%	$75.1702	$75.17	$75.15	$75.20
Purchase #5	$188.76	11.836%	$211.1016	$211.10	$211.10	$211.10
Purchase #6	$212.41	12.197%	$238.3176	$238.32	$238.30	$238.30
Purchase #7	$186.90	4.411%	$195.1442	$195.14	$195.15	$195.10
7 purchase totals =	$1,199.99		$1,300.9688	$1,300.96	$1,300.90	$1,300.90