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	$234.73	12.151%	$263.252	$263.25	$263.25	$263.30
Purchase #2	$20.92	4.309%	$21.8214	$21.82	$21.80	$21.80
Purchase #3	$219.75	4.603%	$229.8651	$229.87	$229.85	$229.90
Purchase #4	$115.78	10.567%	$128.0145	$128.01	$128.00	$128.00
Purchase #5	$129.43	12.603%	$145.7421	$145.74	$145.75	$145.70
Purchase #6	$94.29	9.276%	$103.0363	$103.04	$103.05	$103.00
Purchase #7	$48.38	10.441%	$53.4314	$53.43	$53.45	$53.40
7 purchase totals =	$863.28		$945.1628	$945.16	$945.15	$945.10