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	$43.46	4.467%	$45.4014	$45.40	$45.40	$45.40
Purchase #2	$247.55	11.144%	$275.137	$275.14	$275.15	$275.10
Purchase #3	$226.77	8.676%	$246.4446	$246.44	$246.45	$246.40
Purchase #4	$95.27	8.597%	$103.4604	$103.46	$103.45	$103.50
Purchase #5	$101.70	10.554%	$112.4334	$112.43	$112.45	$112.40
Purchase #6	$72.90	13.536%	$82.7677	$82.77	$82.75	$82.80
Purchase #7	$142.54	12.744%	$160.7053	$160.71	$160.70	$160.70
7 purchase totals =	$930.19		$1,026.3498	$1,026.35	$1,026.35	$1,026.30