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	$158.33	9.103%	$172.7428	$172.74	$172.75	$172.70
Purchase #2	$142.78	12.376%	$160.4505	$160.45	$160.45	$160.50
Purchase #3	$207.76	13.316%	$235.4253	$235.43	$235.45	$235.40
Purchase #4	$71.80	6.757%	$76.6515	$76.65	$76.65	$76.70
Purchase #5	$72.83	13.377%	$82.5725	$82.57	$82.55	$82.60
Purchase #6	$167.80	3.706%	$174.0187	$174.02	$174.00	$174.00
Purchase #7	$200.37	12.321%	$225.0576	$225.06	$225.05	$225.10
7 purchase totals =	$1,021.67		$1,126.9189	$1,126.92	$1,126.90	$1,127.00