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	$105.37	9.788%	$115.6836	$115.68	$115.70	$115.70
Purchase #2	$25.51	10.233%	$28.1204	$28.12	$28.10	$28.10
Purchase #3	$151.91	13.757%	$172.8083	$172.81	$172.80	$172.80
Purchase #4	$221.73	11.132%	$246.413	$246.41	$246.40	$246.40
Purchase #5	$97.89	13.656%	$111.2579	$111.26	$111.25	$111.30
Purchase #6	$225.32	4.506%	$235.4729	$235.47	$235.45	$235.50
Purchase #7	$104.97	3.360%	$108.497	$108.50	$108.50	$108.50
7 purchase totals =	$932.70		$1,018.2531	$1,018.25	$1,018.20	$1,018.30