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	$90.54	12.554%	$101.9064	$101.91	$101.90	$101.90
Purchase #2	$216.72	9.235%	$236.7341	$236.73	$236.75	$236.70
Purchase #3	$124.29	5.666%	$131.3323	$131.33	$131.35	$131.30
Purchase #4	$156.88	13.676%	$178.3349	$178.33	$178.35	$178.30
Purchase #5	$184.83	3.135%	$190.6244	$190.62	$190.60	$190.60
Purchase #6	$231.29	5.234%	$243.3957	$243.40	$243.40	$243.40
Purchase #7	$18.96	11.796%	$21.1965	$21.20	$21.20	$21.20
7 purchase totals =	$1,023.51		$1,103.5243	$1,103.52	$1,103.55	$1,103.40