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	$156.64	10.735%	$173.4553	$173.46	$173.45	$173.50
Purchase #2	$53.94	8.455%	$58.5006	$58.50	$58.50	$58.50
Purchase #3	$76.36	8.289%	$82.6895	$82.69	$82.70	$82.70
Purchase #4	$105.96	13.309%	$120.0622	$120.06	$120.05	$120.10
Purchase #5	$139.86	13.330%	$158.5033	$158.50	$158.50	$158.50
Purchase #6	$176.86	11.197%	$196.663	$196.66	$196.65	$196.70
Purchase #7	$41.68	11.656%	$46.5382	$46.54	$46.55	$46.50
7 purchase totals =	$751.30		$836.4121	$836.41	$836.40	$836.50