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	$196.27	13.549%	$222.8626	$222.86	$222.85	$222.90
Purchase #2	$238.78	10.859%	$264.7091	$264.71	$264.70	$264.70
Purchase #3	$175.97	8.288%	$190.5544	$190.55	$190.55	$190.60
Purchase #4	$83.35	9.349%	$91.1424	$91.14	$91.15	$91.10
Purchase #5	$114.34	12.735%	$128.9012	$128.90	$128.90	$128.90
Purchase #6	$135.74	10.618%	$150.1529	$150.15	$150.15	$150.20
Purchase #7	$60.72	12.550%	$68.3404	$68.34	$68.35	$68.30
7 purchase totals =	$1,005.17		$1,116.6630	$1,116.65	$1,116.65	$1,116.70