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	$37.59	9.162%	$41.034	$41.03	$41.05	$41.00
Purchase #2	$101.49	12.699%	$114.3782	$114.38	$114.40	$114.40
Purchase #3	$83.25	3.207%	$85.9198	$85.92	$85.90	$85.90
Purchase #4	$142.72	6.322%	$151.7428	$151.74	$151.75	$151.70
Purchase #5	$218.78	4.352%	$228.3013	$228.30	$228.30	$228.30
Purchase #6	$184.62	5.790%	$195.3095	$195.31	$195.30	$195.30
Purchase #7	$33.72	4.626%	$35.2799	$35.28	$35.30	$35.30
7 purchase totals =	$802.17		$851.9655	$851.96	$852.00	$851.90