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	$95.71	13.209%	$108.3523	$108.35	$108.35	$108.40
Purchase #2	$175.84	13.851%	$200.1956	$200.20	$200.20	$200.20
Purchase #3	$146.51	10.860%	$162.421	$162.42	$162.40	$162.40
Purchase #4	$73.54	10.678%	$81.3926	$81.39	$81.40	$81.40
Purchase #5	$248.55	6.397%	$264.4497	$264.45	$264.45	$264.40
Purchase #6	$157.27	9.630%	$172.4151	$172.42	$172.40	$172.40
Purchase #7	$243.91	9.459%	$266.9814	$266.98	$267.00	$267.00
7 purchase totals =	$1,141.33		$1,256.2077	$1,256.21	$1,256.20	$1,256.20