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	$151.79	5.529%	$160.1825	$160.18	$160.20	$160.20
Purchase #2	$169.61	6.446%	$180.5431	$180.54	$180.55	$180.50
Purchase #3	$78.26	13.324%	$88.6874	$88.69	$88.70	$88.70
Purchase #4	$119.94	13.795%	$136.4857	$136.49	$136.50	$136.50
Purchase #5	$164.50	4.512%	$171.9222	$171.92	$171.90	$171.90
Purchase #6	$230.63	12.459%	$259.3642	$259.36	$259.35	$259.40
Purchase #7	$19.96	11.835%	$22.3223	$22.32	$22.30	$22.30
7 purchase totals =	$934.69		$1,019.5074	$1,019.50	$1,019.50	$1,019.50