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	$247.31	6.253%	$262.7743	$262.77	$262.75	$262.80
Purchase #2	$129.36	10.183%	$142.5327	$142.53	$142.55	$142.50
Purchase #3	$80.81	12.425%	$90.8506	$90.85	$90.85	$90.90
Purchase #4	$63.42	4.626%	$66.3538	$66.35	$66.35	$66.40
Purchase #5	$116.52	11.267%	$129.6483	$129.65	$129.65	$129.60
Purchase #6	$145.34	10.432%	$160.5019	$160.50	$160.50	$160.50
Purchase #7	$59.33	4.651%	$62.0894	$62.09	$62.10	$62.10
7 purchase totals =	$842.09		$914.7510	$914.74	$914.75	$914.80