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	$70.86	5.538%	$74.7842	$74.78	$74.80	$74.80
Purchase #2	$167.89	4.166%	$174.8843	$174.88	$174.90	$174.90
Purchase #3	$211.38	12.679%	$238.1809	$238.18	$238.20	$238.20
Purchase #4	$153.79	8.490%	$166.8468	$166.85	$166.85	$166.80
Purchase #5	$99.67	10.222%	$109.8583	$109.86	$109.85	$109.90
Purchase #6	$62.34	7.301%	$66.8914	$66.89	$66.90	$66.90
Purchase #7	$164.39	13.577%	$186.7092	$186.71	$186.70	$186.70
7 purchase totals =	$930.32		$1,018.1551	$1,018.15	$1,018.20	$1,018.20