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	$95.45	4.714%	$99.9495	$99.95	$99.95	$99.90
Purchase #2	$188.95	9.767%	$207.4047	$207.40	$207.40	$207.40
Purchase #3	$119.89	6.413%	$127.5785	$127.58	$127.60	$127.60
Purchase #4	$16.38	10.250%	$18.059	$18.06	$18.05	$18.10
Purchase #5	$204.32	9.467%	$223.663	$223.66	$223.65	$223.70
Purchase #6	$189.78	5.868%	$200.9163	$200.92	$200.90	$200.90
Purchase #7	$175.32	10.228%	$193.2517	$193.25	$193.25	$193.30
7 purchase totals =	$990.09		$1,070.8227	$1,070.82	$1,070.80	$1,070.90