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	$210.62	8.663%	$228.866	$228.87	$228.85	$228.90
Purchase #2	$168.53	9.317%	$184.2319	$184.23	$184.25	$184.20
Purchase #3	$152.36	10.667%	$168.6122	$168.61	$168.60	$168.60
Purchase #4	$98.82	5.795%	$104.5466	$104.55	$104.55	$104.50
Purchase #5	$122.51	7.155%	$131.2756	$131.28	$131.30	$131.30
Purchase #6	$190.82	11.762%	$213.2642	$213.26	$213.25	$213.30
Purchase #7	$48.96	3.620%	$50.7324	$50.73	$50.75	$50.70
7 purchase totals =	$992.62		$1,081.5289	$1,081.53	$1,081.55	$1,081.50