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	$108.80	10.447%	$120.1663	$120.17	$120.15	$120.20
Purchase #2	$95.87	11.157%	$106.5662	$106.57	$106.55	$106.60
Purchase #3	$218.82	4.839%	$229.4087	$229.41	$229.40	$229.40
Purchase #4	$99.33	10.334%	$109.5948	$109.59	$109.60	$109.60
Purchase #5	$53.82	9.413%	$58.8861	$58.89	$58.90	$58.90
Purchase #6	$148.50	13.744%	$168.9098	$168.91	$168.90	$168.90
Purchase #7	$243.95	12.302%	$273.9607	$273.96	$273.95	$274.00
7 purchase totals =	$969.09		$1,067.4926	$1,067.50	$1,067.45	$1,067.60