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	$245.78	7.650%	$264.5822	$264.58	$264.60	$264.60
Purchase #2	$220.78	3.695%	$228.9378	$228.94	$228.95	$228.90
Purchase #3	$149.27	13.278%	$169.0901	$169.09	$169.10	$169.10
Purchase #4	$92.35	12.371%	$103.7746	$103.77	$103.75	$103.80
Purchase #5	$219.51	3.503%	$227.1994	$227.20	$227.20	$227.20
Purchase #6	$30.59	5.650%	$32.3183	$32.32	$32.30	$32.30
Purchase #7	$37.97	6.135%	$40.2995	$40.30	$40.30	$40.30
7 purchase totals =	$996.25		$1,066.2019	$1,066.20	$1,066.20	$1,066.20