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	$224.79	6.279%	$238.9046	$238.90	$238.90	$238.90
Purchase #2	$244.58	6.763%	$261.1209	$261.12	$261.10	$261.10
Purchase #3	$119.80	6.420%	$127.4912	$127.49	$127.50	$127.50
Purchase #4	$98.81	7.253%	$105.9767	$105.98	$106.00	$106.00
Purchase #5	$184.50	3.773%	$191.4612	$191.46	$191.45	$191.50
Purchase #6	$175.95	11.113%	$195.5033	$195.50	$195.50	$195.50
Purchase #7	$175.26	13.839%	$199.5142	$199.51	$199.50	$199.50
7 purchase totals =	$1,223.69		$1,319.9721	$1,319.96	$1,319.95	$1,320.00