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	$210.73	10.345%	$232.53	$232.53	$232.55	$232.50
Purchase #2	$96.82	9.829%	$106.3364	$106.34	$106.35	$106.30
Purchase #3	$78.36	3.805%	$81.3416	$81.34	$81.35	$81.30
Purchase #4	$116.52	9.736%	$127.8644	$127.86	$127.85	$127.90
Purchase #5	$58.88	9.619%	$64.5437	$64.54	$64.55	$64.50
Purchase #6	$38.33	11.514%	$42.7433	$42.74	$42.75	$42.70
Purchase #7	$198.87	8.827%	$216.4243	$216.42	$216.40	$216.40
7 purchase totals =	$798.51		$871.7837	$871.77	$871.80	$871.60