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	$52.92	6.472%	$56.345	$56.35	$56.35	$56.30
Purchase #2	$148.34	9.419%	$162.3121	$162.31	$162.30	$162.30
Purchase #3	$213.82	6.564%	$227.8551	$227.86	$227.85	$227.90
Purchase #4	$10.71	13.569%	$12.1632	$12.16	$12.15	$12.20
Purchase #5	$45.31	7.213%	$48.5782	$48.58	$48.60	$48.60
Purchase #6	$99.95	7.681%	$107.6272	$107.63	$107.65	$107.60
Purchase #7	$133.96	13.831%	$152.488	$152.49	$152.50	$152.50
7 purchase totals =	$705.01		$767.3688	$767.38	$767.40	$767.40