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	$149.54	5.499%	$157.7632	$157.76	$157.75	$157.80
Purchase #2	$9.81	11.416%	$10.9299	$10.93	$10.95	$10.90
Purchase #3	$40.59	8.121%	$43.8863	$43.89	$43.90	$43.90
Purchase #4	$121.36	12.543%	$136.5822	$136.58	$136.60	$136.60
Purchase #5	$165.50	9.674%	$181.5105	$181.51	$181.50	$181.50
Purchase #6	$113.81	3.729%	$118.054	$118.05	$118.05	$118.10
Purchase #7	$172.73	13.728%	$196.4424	$196.44	$196.45	$196.40
7 purchase totals =	$773.34		$845.1685	$845.16	$845.20	$845.20