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	$147.48	11.359%	$164.2323	$164.23	$164.25	$164.20
Purchase #2	$236.85	6.349%	$251.8876	$251.89	$251.90	$251.90
Purchase #3	$70.46	7.214%	$75.543	$75.54	$75.55	$75.50
Purchase #4	$186.81	12.150%	$209.5074	$209.51	$209.50	$209.50
Purchase #5	$131.36	11.610%	$146.6109	$146.61	$146.60	$146.60
Purchase #6	$77.91	5.863%	$82.4779	$82.48	$82.50	$82.50
Purchase #7	$76.90	4.183%	$80.1167	$80.12	$80.10	$80.10
7 purchase totals =	$927.77		$1,010.3758	$1,010.38	$1,010.40	$1,010.30