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	$59.30	3.144%	$61.1644	$61.16	$61.15	$61.20
Purchase #2	$65.34	10.376%	$72.1197	$72.12	$72.10	$72.10
Purchase #3	$126.93	11.502%	$141.5295	$141.53	$141.55	$141.50
Purchase #4	$68.34	12.850%	$77.1217	$77.12	$77.10	$77.10
Purchase #5	$210.83	9.242%	$230.3149	$230.31	$230.30	$230.30
Purchase #6	$102.66	9.812%	$112.733	$112.73	$112.75	$112.70
Purchase #7	$90.90	3.380%	$93.9724	$93.97	$93.95	$94.00
7 purchase totals =	$724.30		$788.9556	$788.94	$788.90	$788.90