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	$211.84	6.475%	$225.5566	$225.56	$225.55	$225.60
Purchase #2	$215.47	12.505%	$242.4145	$242.41	$242.40	$242.40
Purchase #3	$156.26	12.572%	$175.905	$175.91	$175.90	$175.90
Purchase #4	$165.97	5.844%	$175.6693	$175.67	$175.65	$175.70
Purchase #5	$82.75	4.448%	$86.4307	$86.43	$86.45	$86.40
Purchase #6	$234.40	10.307%	$258.5596	$258.56	$258.55	$258.60
Purchase #7	$244.46	8.346%	$264.8626	$264.86	$264.85	$264.90
7 purchase totals =	$1,311.15		$1,429.3983	$1,429.40	$1,429.35	$1,429.50