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	$221.87	7.119%	$237.6649	$237.66	$237.65	$237.70
Purchase #2	$24.26	11.373%	$27.0191	$27.02	$27.00	$27.00
Purchase #3	$234.31	12.425%	$263.423	$263.42	$263.40	$263.40
Purchase #4	$247.31	11.308%	$275.2758	$275.28	$275.30	$275.30
Purchase #5	$66.67	8.633%	$72.4256	$72.43	$72.45	$72.40
Purchase #6	$162.47	3.805%	$168.652	$168.65	$168.65	$168.70
Purchase #7	$101.83	4.860%	$106.7789	$106.78	$106.80	$106.80
7 purchase totals =	$1,058.72		$1,151.2393	$1,151.24	$1,151.25	$1,151.30