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	$199.61	7.128%	$213.8382	$213.84	$213.85	$213.80
Purchase #2	$68.94	11.420%	$76.8129	$76.81	$76.80	$76.80
Purchase #3	$202.32	9.609%	$221.7609	$221.76	$221.75	$221.80
Purchase #4	$90.43	11.133%	$100.4976	$100.50	$100.50	$100.50
Purchase #5	$98.28	7.181%	$105.3375	$105.34	$105.35	$105.30
Purchase #6	$79.49	12.120%	$89.1242	$89.12	$89.10	$89.10
Purchase #7	$218.71	7.412%	$234.9208	$234.92	$234.90	$234.90
7 purchase totals =	$957.78		$1,042.2921	$1,042.29	$1,042.25	$1,042.20