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	$38.32	13.749%	$43.5886	$43.59	$43.60	$43.60
Purchase #2	$185.41	10.587%	$205.0394	$205.04	$205.05	$205.00
Purchase #3	$209.33	13.201%	$236.9637	$236.96	$236.95	$237.00
Purchase #4	$49.49	12.259%	$55.557	$55.56	$55.55	$55.60
Purchase #5	$139.26	9.760%	$152.8518	$152.85	$152.85	$152.90
Purchase #6	$93.98	13.645%	$106.8036	$106.80	$106.80	$106.80
Purchase #7	$237.74	9.544%	$260.4299	$260.43	$260.45	$260.40
7 purchase totals =	$953.53		$1,061.2340	$1,061.23	$1,061.25	$1,061.30