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	$32.46	7.728%	$34.9685	$34.97	$34.95	$35.00
Purchase #2	$49.37	7.570%	$53.1073	$53.11	$53.10	$53.10
Purchase #3	$53.77	3.791%	$55.8084	$55.81	$55.80	$55.80
Purchase #4	$72.82	7.558%	$78.3237	$78.32	$78.30	$78.30
Purchase #5	$247.82	6.309%	$263.455	$263.46	$263.45	$263.50
Purchase #6	$98.25	8.522%	$106.6229	$106.62	$106.60	$106.60
Purchase #7	$127.30	8.445%	$138.0505	$138.05	$138.05	$138.10
7 purchase totals =	$681.79		$730.3363	$730.34	$730.25	$730.40