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	$10.50	7.811%	$11.3202	$11.32	$11.30	$11.30
Purchase #2	$119.64	12.512%	$134.6094	$134.61	$134.60	$134.60
Purchase #3	$40.64	11.738%	$45.4103	$45.41	$45.40	$45.40
Purchase #4	$22.74	7.685%	$24.4876	$24.49	$24.50	$24.50
Purchase #5	$37.57	6.759%	$40.1094	$40.11	$40.10	$40.10
Purchase #6	$203.63	6.535%	$216.9372	$216.94	$216.95	$216.90
Purchase #7	$80.54	11.267%	$89.6144	$89.61	$89.60	$89.60
7 purchase totals =	$515.26		$562.4885	$562.49	$562.45	$562.40