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	$105.39	5.141%	$110.8081	$110.81	$110.80	$110.80
Purchase #2	$143.68	4.323%	$149.8913	$149.89	$149.90	$149.90
Purchase #3	$125.31	4.173%	$130.5392	$130.54	$130.55	$130.50
Purchase #4	$103.80	5.282%	$109.2827	$109.28	$109.30	$109.30
Purchase #5	$38.27	5.824%	$40.4988	$40.50	$40.50	$40.50
Purchase #6	$138.72	13.103%	$156.8965	$156.90	$156.90	$156.90
Purchase #7	$194.57	11.305%	$216.5661	$216.57	$216.55	$216.60
7 purchase totals =	$849.74		$914.4827	$914.49	$914.50	$914.50