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	$130.83	10.532%	$144.609	$144.61	$144.60	$144.60
Purchase #2	$189.61	3.228%	$195.7306	$195.73	$195.75	$195.70
Purchase #3	$91.27	11.676%	$101.9267	$101.93	$101.95	$101.90
Purchase #4	$132.73	7.195%	$142.2799	$142.28	$142.30	$142.30
Purchase #5	$83.74	8.743%	$91.0614	$91.06	$91.05	$91.10
Purchase #6	$41.47	9.369%	$45.3553	$45.36	$45.35	$45.40
Purchase #7	$139.25	8.158%	$150.61	$150.61	$150.60	$150.60
7 purchase totals =	$808.90		$871.5729	$871.58	$871.60	$871.60