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	$157.92	9.494%	$172.9129	$172.91	$172.90	$172.90
Purchase #2	$244.33	11.753%	$273.0461	$273.05	$273.05	$273.00
Purchase #3	$192.38	4.526%	$201.0871	$201.09	$201.10	$201.10
Purchase #4	$164.99	3.373%	$170.5551	$170.56	$170.55	$170.60
Purchase #5	$99.41	11.695%	$111.036	$111.04	$111.05	$111.00
Purchase #6	$83.32	7.715%	$89.7481	$89.75	$89.75	$89.70
Purchase #7	$101.36	8.361%	$109.8347	$109.83	$109.85	$109.80
7 purchase totals =	$1,043.71		$1,128.2200	$1,128.23	$1,128.25	$1,128.10