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	$87.60	5.353%	$92.2892	$92.29	$92.30	$92.30
Purchase #2	$224.32	13.575%	$254.7714	$254.77	$254.75	$254.80
Purchase #3	$237.70	13.690%	$270.2411	$270.24	$270.25	$270.20
Purchase #4	$82.72	8.588%	$89.824	$89.82	$89.80	$89.80
Purchase #5	$31.65	4.767%	$33.1588	$33.16	$33.15	$33.20
Purchase #6	$114.48	8.215%	$123.8845	$123.88	$123.90	$123.90
Purchase #7	$67.36	6.244%	$71.566	$71.57	$71.55	$71.60
7 purchase totals =	$845.83		$935.7350	$935.73	$935.70	$935.80