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	$60.94	11.776%	$68.1163	$68.12	$68.10	$68.10
Purchase #2	$102.76	6.807%	$109.7549	$109.75	$109.75	$109.80
Purchase #3	$77.83	13.483%	$88.3238	$88.32	$88.30	$88.30
Purchase #4	$212.66	13.522%	$241.4159	$241.42	$241.40	$241.40
Purchase #5	$157.96	4.617%	$165.253	$165.25	$165.25	$165.30
Purchase #6	$78.44	13.737%	$89.2153	$89.22	$89.20	$89.20
Purchase #7	$196.39	13.546%	$222.993	$222.99	$223.00	$223.00
7 purchase totals =	$886.98		$985.0722	$985.07	$985.00	$985.10