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	$84.99	5.472%	$89.6407	$89.64	$89.65	$89.60
Purchase #2	$108.55	7.127%	$116.2864	$116.29	$116.30	$116.30
Purchase #3	$168.44	10.540%	$186.1936	$186.19	$186.20	$186.20
Purchase #4	$199.61	11.276%	$222.118	$222.12	$222.10	$222.10
Purchase #5	$230.55	5.294%	$242.7553	$242.76	$242.75	$242.80
Purchase #6	$165.25	10.333%	$182.3253	$182.33	$182.35	$182.30
Purchase #7	$51.48	10.578%	$56.9256	$56.93	$56.95	$56.90
7 purchase totals =	$1,008.87		$1,096.2449	$1,096.26	$1,096.30	$1,096.20