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	$98.27	3.742%	$101.9473	$101.95	$101.95	$101.90
Purchase #2	$51.76	9.725%	$56.7937	$56.79	$56.80	$56.80
Purchase #3	$37.51	13.144%	$42.4403	$42.44	$42.45	$42.40
Purchase #4	$156.87	3.368%	$162.1534	$162.15	$162.15	$162.20
Purchase #5	$29.90	9.444%	$32.7238	$32.72	$32.70	$32.70
Purchase #6	$126.35	11.744%	$141.1885	$141.19	$141.20	$141.20
Purchase #7	$146.38	9.381%	$160.1119	$160.11	$160.10	$160.10
7 purchase totals =	$647.04		$697.3589	$697.35	$697.35	$697.30