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	$135.31	4.294%	$141.1202	$141.12	$141.10	$141.10
Purchase #2	$93.99	11.717%	$105.0028	$105.00	$105.00	$105.00
Purchase #3	$73.64	6.813%	$78.6571	$78.66	$78.65	$78.70
Purchase #4	$53.65	10.374%	$59.2157	$59.22	$59.20	$59.20
Purchase #5	$152.73	13.243%	$172.956	$172.96	$172.95	$173.00
Purchase #6	$47.34	8.383%	$51.3085	$51.31	$51.30	$51.30
Purchase #7	$222.95	6.555%	$237.5644	$237.56	$237.55	$237.60
7 purchase totals =	$779.61		$845.8247	$845.83	$845.75	$845.90