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	$174.68	4.272%	$182.1423	$182.14	$182.15	$182.10
Purchase #2	$96.49	9.770%	$105.9171	$105.92	$105.90	$105.90
Purchase #3	$81.66	4.666%	$85.4703	$85.47	$85.45	$85.50
Purchase #4	$250.32	10.612%	$276.884	$276.88	$276.90	$276.90
Purchase #5	$213.35	7.283%	$228.8883	$228.89	$228.90	$228.90
Purchase #6	$111.45	12.221%	$125.0703	$125.07	$125.05	$125.10
Purchase #7	$72.66	7.187%	$77.8821	$77.88	$77.90	$77.90
7 purchase totals =	$1,000.61		$1,082.2544	$1,082.25	$1,082.25	$1,082.30