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	$118.43	10.310%	$130.6401	$130.64	$130.65	$130.60
Purchase #2	$134.91	13.525%	$153.1566	$153.16	$153.15	$153.20
Purchase #3	$190.97	10.488%	$210.9989	$211.00	$211.00	$211.00
Purchase #4	$117.71	4.692%	$123.233	$123.23	$123.25	$123.20
Purchase #5	$159.36	6.148%	$169.1575	$169.16	$169.15	$169.20
Purchase #6	$105.28	3.784%	$109.2638	$109.26	$109.25	$109.30
Purchase #7	$38.54	11.437%	$42.9478	$42.95	$42.95	$42.90
7 purchase totals =	$865.20		$939.3977	$939.40	$939.40	$939.40