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	$175.39	7.292%	$188.1794	$188.18	$188.20	$188.20
Purchase #2	$229.99	12.827%	$259.4908	$259.49	$259.50	$259.50
Purchase #3	$99.39	11.711%	$111.0296	$111.03	$111.05	$111.00
Purchase #4	$69.34	5.134%	$72.8999	$72.90	$72.90	$72.90
Purchase #5	$201.57	9.515%	$220.7494	$220.75	$220.75	$220.70
Purchase #6	$79.69	3.192%	$82.2337	$82.23	$82.25	$82.20
Purchase #7	$191.55	7.847%	$206.5809	$206.58	$206.60	$206.60
7 purchase totals =	$1,046.92		$1,141.1637	$1,141.16	$1,141.25	$1,141.10