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	$102.95	7.871%	$111.0532	$111.05	$111.05	$111.10
Purchase #2	$41.55	6.476%	$44.2408	$44.24	$44.25	$44.20
Purchase #3	$47.86	10.219%	$52.7508	$52.75	$52.75	$52.80
Purchase #4	$229.59	3.454%	$237.52	$237.52	$237.50	$237.50
Purchase #5	$60.62	11.281%	$67.4585	$67.46	$67.45	$67.50
Purchase #6	$249.97	12.757%	$281.8587	$281.86	$281.85	$281.90
Purchase #7	$18.50	5.796%	$19.5723	$19.57	$19.55	$19.60
7 purchase totals =	$751.04		$814.4543	$814.45	$814.40	$814.60