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	$124.37	5.664%	$131.4143	$131.41	$131.40	$131.40
Purchase #2	$222.87	9.137%	$243.2336	$243.23	$243.25	$243.20
Purchase #3	$230.57	4.174%	$240.194	$240.19	$240.20	$240.20
Purchase #4	$181.60	12.399%	$204.1166	$204.12	$204.10	$204.10
Purchase #5	$66.25	9.171%	$72.3258	$72.33	$72.35	$72.30
Purchase #6	$14.74	13.828%	$16.7782	$16.78	$16.80	$16.80
Purchase #7	$155.96	5.466%	$164.4848	$164.48	$164.50	$164.50
7 purchase totals =	$996.36		$1,072.5473	$1,072.54	$1,072.60	$1,072.50