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	$90.80	10.606%	$100.4302	$100.43	$100.45	$100.40
Purchase #2	$37.36	3.465%	$38.6545	$38.65	$38.65	$38.70
Purchase #3	$35.46	4.658%	$37.1117	$37.11	$37.10	$37.10
Purchase #4	$65.58	11.850%	$73.3512	$73.35	$73.35	$73.40
Purchase #5	$182.82	3.557%	$189.3229	$189.32	$189.30	$189.30
Purchase #6	$153.50	10.134%	$169.0557	$169.06	$169.05	$169.10
Purchase #7	$139.51	13.507%	$158.3536	$158.35	$158.35	$158.40
7 purchase totals =	$705.03		$766.2798	$766.27	$766.25	$766.40