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	$180.75	12.538%	$203.4124	$203.41	$203.40	$203.40
Purchase #2	$201.26	10.802%	$223.0001	$223.00	$223.00	$223.00
Purchase #3	$10.69	6.398%	$11.3739	$11.37	$11.35	$11.40
Purchase #4	$156.31	9.807%	$171.6393	$171.64	$171.65	$171.60
Purchase #5	$109.89	5.312%	$115.7274	$115.73	$115.75	$115.70
Purchase #6	$174.25	6.504%	$185.5832	$185.58	$185.60	$185.60
Purchase #7	$128.54	7.259%	$137.8707	$137.87	$137.85	$137.90
7 purchase totals =	$961.69		$1,048.6070	$1,048.60	$1,048.60	$1,048.60