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	$152.69	7.518%	$164.1692	$164.17	$164.15	$164.20
Purchase #2	$49.33	6.430%	$52.5019	$52.50	$52.50	$52.50
Purchase #3	$102.28	9.535%	$112.0324	$112.03	$112.05	$112.00
Purchase #4	$29.99	13.495%	$34.0372	$34.04	$34.05	$34.00
Purchase #5	$28.47	7.278%	$30.542	$30.54	$30.55	$30.50
Purchase #6	$94.33	5.548%	$99.5634	$99.56	$99.55	$99.60
Purchase #7	$11.31	10.719%	$12.5223	$12.52	$12.50	$12.50
7 purchase totals =	$468.40		$505.3684	$505.36	$505.35	$505.30