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	$73.35	13.760%	$83.443	$83.44	$83.45	$83.40
Purchase #2	$71.59	7.568%	$77.0079	$77.01	$77.00	$77.00
Purchase #3	$84.80	11.384%	$94.4536	$94.45	$94.45	$94.50
Purchase #4	$244.83	13.260%	$277.2945	$277.29	$277.30	$277.30
Purchase #5	$228.86	13.269%	$259.2274	$259.23	$259.25	$259.20
Purchase #6	$90.57	12.555%	$101.9411	$101.94	$101.95	$101.90
Purchase #7	$167.51	9.539%	$183.4888	$183.49	$183.50	$183.50
7 purchase totals =	$961.51		$1,076.8563	$1,076.85	$1,076.90	$1,076.80