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	$157.39	5.827%	$166.5611	$166.56	$166.55	$166.60
Purchase #2	$58.81	6.227%	$62.4721	$62.47	$62.45	$62.50
Purchase #3	$228.39	12.222%	$256.3038	$256.30	$256.30	$256.30
Purchase #4	$85.46	5.535%	$90.1902	$90.19	$90.20	$90.20
Purchase #5	$210.71	9.139%	$229.9668	$229.97	$229.95	$230.00
Purchase #6	$211.44	3.587%	$219.0244	$219.02	$219.00	$219.00
Purchase #7	$115.72	3.589%	$119.8732	$119.87	$119.85	$119.90
7 purchase totals =	$1,067.92		$1,144.3916	$1,144.38	$1,144.30	$1,144.50