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	$117.89	6.155%	$125.1461	$125.15	$125.15	$125.10
Purchase #2	$35.66	11.514%	$39.7659	$39.77	$39.75	$39.80
Purchase #3	$174.39	12.562%	$196.2969	$196.30	$196.30	$196.30
Purchase #4	$116.33	9.210%	$127.044	$127.04	$127.05	$127.00
Purchase #5	$49.94	4.667%	$52.2707	$52.27	$52.25	$52.30
Purchase #6	$15.49	12.593%	$17.4407	$17.44	$17.45	$17.40
Purchase #7	$191.61	10.243%	$211.2366	$211.24	$211.25	$211.20
7 purchase totals =	$701.31		$769.2009	$769.21	$769.20	$769.10