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	$57.70	7.239%	$61.8769	$61.88	$61.90	$61.90
Purchase #2	$45.38	10.581%	$50.1817	$50.18	$50.20	$50.20
Purchase #3	$66.61	8.568%	$72.3171	$72.32	$72.30	$72.30
Purchase #4	$162.42	4.571%	$169.8442	$169.84	$169.85	$169.80
Purchase #5	$50.73	12.756%	$57.2011	$57.20	$57.20	$57.20
Purchase #6	$104.62	11.385%	$116.531	$116.53	$116.55	$116.50
Purchase #7	$196.78	10.484%	$217.4104	$217.41	$217.40	$217.40
7 purchase totals =	$684.24		$745.3624	$745.36	$745.40	$745.30