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	$141.92	10.872%	$157.3495	$157.35	$157.35	$157.30
Purchase #2	$162.54	13.822%	$185.0063	$185.01	$185.00	$185.00
Purchase #3	$57.46	12.691%	$64.7522	$64.75	$64.75	$64.80
Purchase #4	$81.45	11.362%	$90.7043	$90.70	$90.70	$90.70
Purchase #5	$152.40	11.786%	$170.3619	$170.36	$170.35	$170.40
Purchase #6	$85.60	4.179%	$89.1772	$89.18	$89.20	$89.20
Purchase #7	$224.40	8.626%	$243.7567	$243.76	$243.75	$243.80
7 purchase totals =	$905.77		$1,001.1081	$1,001.11	$1,001.10	$1,001.20