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	$167.55	4.328%	$174.8016	$174.80	$174.80	$174.80
Purchase #2	$120.41	9.208%	$131.4974	$131.50	$131.50	$131.50
Purchase #3	$222.85	11.213%	$247.8382	$247.84	$247.85	$247.80
Purchase #4	$6.56	12.234%	$7.3626	$7.36	$7.35	$7.40
Purchase #5	$141.87	8.128%	$153.4012	$153.40	$153.40	$153.40
Purchase #6	$98.26	4.874%	$103.0492	$103.05	$103.05	$103.00
Purchase #7	$228.31	7.528%	$245.4972	$245.50	$245.50	$245.50
7 purchase totals =	$985.81		$1,063.4474	$1,063.45	$1,063.45	$1,063.40