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	$210.34	5.739%	$222.4114	$222.41	$222.40	$222.40
Purchase #2	$206.25	3.384%	$213.2295	$213.23	$213.25	$213.20
Purchase #3	$25.40	12.238%	$28.5085	$28.51	$28.50	$28.50
Purchase #4	$27.42	6.763%	$29.2744	$29.27	$29.25	$29.30
Purchase #5	$111.26	11.359%	$123.898	$123.90	$123.90	$123.90
Purchase #6	$171.67	9.760%	$188.425	$188.43	$188.45	$188.40
Purchase #7	$235.55	3.179%	$243.0381	$243.04	$243.05	$243.00
7 purchase totals =	$987.89		$1,048.7849	$1,048.79	$1,048.80	$1,048.70