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	$229.27	7.223%	$245.8302	$245.83	$245.85	$245.80
Purchase #2	$70.69	3.452%	$73.1302	$73.13	$73.15	$73.10
Purchase #3	$114.63	3.734%	$118.9103	$118.91	$118.90	$118.90
Purchase #4	$250.88	12.647%	$282.6088	$282.61	$282.60	$282.60
Purchase #5	$173.75	11.761%	$194.1847	$194.18	$194.20	$194.20
Purchase #6	$62.38	7.269%	$66.9144	$66.91	$66.90	$66.90
Purchase #7	$211.96	3.294%	$218.942	$218.94	$218.95	$218.90
7 purchase totals =	$1,113.56		$1,200.5206	$1,200.51	$1,200.55	$1,200.40