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	$140.71	7.651%	$151.4757	$151.48	$151.50	$151.50
Purchase #2	$168.44	5.761%	$178.1438	$178.14	$178.15	$178.10
Purchase #3	$187.61	13.221%	$212.4139	$212.41	$212.40	$212.40
Purchase #4	$160.29	8.243%	$173.5027	$173.50	$173.50	$173.50
Purchase #5	$189.89	3.680%	$196.878	$196.88	$196.90	$196.90
Purchase #6	$130.88	12.430%	$147.1484	$147.15	$147.15	$147.10
Purchase #7	$30.33	3.805%	$31.4841	$31.48	$31.50	$31.50
7 purchase totals =	$1,008.15		$1,091.0466	$1,091.04	$1,091.10	$1,091.00