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	$141.94	8.169%	$153.5351	$153.54	$153.55	$153.50
Purchase #2	$146.89	8.797%	$159.8119	$159.81	$159.80	$159.80
Purchase #3	$63.27	13.842%	$72.0278	$72.03	$72.05	$72.00
Purchase #4	$86.76	6.395%	$92.3083	$92.31	$92.30	$92.30
Purchase #5	$24.36	3.262%	$25.1546	$25.15	$25.15	$25.20
Purchase #6	$58.78	9.344%	$64.2724	$64.27	$64.25	$64.30
Purchase #7	$81.72	5.520%	$86.2309	$86.23	$86.25	$86.20
7 purchase totals =	$603.72		$653.3410	$653.34	$653.35	$653.30