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	$35.35	5.659%	$37.3505	$37.35	$37.35	$37.40
Purchase #2	$78.95	4.382%	$82.4096	$82.41	$82.40	$82.40
Purchase #3	$40.51	11.777%	$45.2809	$45.28	$45.30	$45.30
Purchase #4	$189.34	12.370%	$212.7614	$212.76	$212.75	$212.80
Purchase #5	$110.95	11.840%	$124.0865	$124.09	$124.10	$124.10
Purchase #6	$117.70	11.501%	$131.2367	$131.24	$131.25	$131.20
Purchase #7	$98.30	4.148%	$102.3775	$102.38	$102.40	$102.40
7 purchase totals =	$671.10		$735.5031	$735.51	$735.55	$735.60