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	$157.27	10.644%	$174.0098	$174.01	$174.00	$174.00
Purchase #2	$137.31	7.155%	$147.1345	$147.13	$147.15	$147.10
Purchase #3	$166.43	8.338%	$180.3069	$180.31	$180.30	$180.30
Purchase #4	$207.29	7.320%	$222.4636	$222.46	$222.45	$222.50
Purchase #5	$142.54	9.368%	$155.8931	$155.89	$155.90	$155.90
Purchase #6	$118.82	11.200%	$132.1278	$132.13	$132.15	$132.10
Purchase #7	$79.71	10.777%	$88.3003	$88.30	$88.30	$88.30
7 purchase totals =	$1,009.37		$1,100.2360	$1,100.23	$1,100.25	$1,100.20