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	$40.40	10.412%	$44.6064	$44.61	$44.60	$44.60
Purchase #2	$51.42	4.783%	$53.8794	$53.88	$53.90	$53.90
Purchase #3	$16.29	11.269%	$18.1257	$18.13	$18.15	$18.10
Purchase #4	$56.61	9.212%	$61.8249	$61.82	$61.80	$61.80
Purchase #5	$67.98	3.851%	$70.5979	$70.60	$70.60	$70.60
Purchase #6	$188.49	12.324%	$211.7195	$211.72	$211.70	$211.70
Purchase #7	$77.29	12.245%	$86.7542	$86.75	$86.75	$86.80
7 purchase totals =	$498.48		$547.5080	$547.51	$547.50	$547.50