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	$119.59	6.281%	$127.1014	$127.10	$127.10	$127.10
Purchase #2	$198.91	6.351%	$211.5428	$211.54	$211.55	$211.50
Purchase #3	$55.65	8.260%	$60.2467	$60.25	$60.25	$60.20
Purchase #4	$239.40	11.741%	$267.508	$267.51	$267.50	$267.50
Purchase #5	$174.75	12.159%	$195.9979	$196.00	$196.00	$196.00
Purchase #6	$159.87	5.161%	$168.1209	$168.12	$168.10	$168.10
Purchase #7	$159.46	6.347%	$169.5809	$169.58	$169.60	$169.60
7 purchase totals =	$1,107.63		$1,200.0986	$1,200.10	$1,200.10	$1,200.00