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	$172.42	9.339%	$188.5223	$188.52	$188.50	$188.50
Purchase #2	$172.79	11.251%	$192.2306	$192.23	$192.25	$192.20
Purchase #3	$192.48	10.366%	$212.4325	$212.43	$212.45	$212.40
Purchase #4	$136.71	11.321%	$152.1869	$152.19	$152.20	$152.20
Purchase #5	$110.33	11.572%	$123.0974	$123.10	$123.10	$123.10
Purchase #6	$51.84	4.854%	$54.3563	$54.36	$54.35	$54.40
Purchase #7	$101.51	4.241%	$105.815	$105.82	$105.80	$105.80
7 purchase totals =	$938.08		$1,028.6410	$1,028.65	$1,028.65	$1,028.60