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	$169.59	13.749%	$192.9069	$192.91	$192.90	$192.90
Purchase #2	$26.47	6.394%	$28.1625	$28.16	$28.15	$28.20
Purchase #3	$196.65	13.838%	$223.8624	$223.86	$223.85	$223.90
Purchase #4	$218.57	9.121%	$238.5058	$238.51	$238.50	$238.50
Purchase #5	$104.89	4.398%	$109.5031	$109.50	$109.50	$109.50
Purchase #6	$24.77	9.683%	$27.1685	$27.17	$27.15	$27.20
Purchase #7	$206.43	7.218%	$221.3301	$221.33	$221.35	$221.30
7 purchase totals =	$947.37		$1,041.4393	$1,041.44	$1,041.40	$1,041.50