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	$35.41	9.292%	$38.7003	$38.70	$38.70	$38.70
Purchase #2	$40.37	11.497%	$45.0113	$45.01	$45.00	$45.00
Purchase #3	$87.58	9.148%	$95.5918	$95.59	$95.60	$95.60
Purchase #4	$150.99	9.851%	$165.864	$165.86	$165.85	$165.90
Purchase #5	$243.38	12.530%	$273.8755	$273.88	$273.90	$273.90
Purchase #6	$200.90	11.146%	$223.2923	$223.29	$223.30	$223.30
Purchase #7	$170.25	7.332%	$182.7327	$182.73	$182.75	$182.70
7 purchase totals =	$928.88		$1,025.0679	$1,025.06	$1,025.10	$1,025.10