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	$222.46	6.656%	$237.2669	$237.27	$237.25	$237.30
Purchase #2	$224.43	9.456%	$245.6521	$245.65	$245.65	$245.70
Purchase #3	$199.26	3.283%	$205.8017	$205.80	$205.80	$205.80
Purchase #4	$146.47	4.151%	$152.55	$152.55	$152.55	$152.60
Purchase #5	$116.69	12.364%	$131.1176	$131.12	$131.10	$131.10
Purchase #6	$68.71	5.653%	$72.5942	$72.59	$72.60	$72.60
Purchase #7	$151.49	5.734%	$160.1764	$160.18	$160.20	$160.20
7 purchase totals =	$1,129.51		$1,205.1589	$1,205.16	$1,205.15	$1,205.30