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	$102.38	7.337%	$109.8916	$109.89	$109.90	$109.90
Purchase #2	$62.33	5.170%	$65.5525	$65.55	$65.55	$65.60
Purchase #3	$247.47	13.851%	$281.7471	$281.75	$281.75	$281.70
Purchase #4	$220.32	3.708%	$228.4895	$228.49	$228.50	$228.50
Purchase #5	$234.98	10.363%	$259.331	$259.33	$259.35	$259.30
Purchase #6	$157.61	7.604%	$169.5947	$169.59	$169.60	$169.60
Purchase #7	$43.66	5.115%	$45.8932	$45.89	$45.90	$45.90
7 purchase totals =	$1,068.75		$1,160.4996	$1,160.49	$1,160.55	$1,160.50