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	$98.30	7.572%	$105.7433	$105.74	$105.75	$105.70
Purchase #2	$169.41	7.106%	$181.4483	$181.45	$181.45	$181.40
Purchase #3	$50.32	7.841%	$54.2656	$54.27	$54.25	$54.30
Purchase #4	$114.63	3.380%	$118.5045	$118.50	$118.50	$118.50
Purchase #5	$67.39	9.159%	$73.5623	$73.56	$73.55	$73.60
Purchase #6	$21.42	13.131%	$24.2327	$24.23	$24.25	$24.20
Purchase #7	$63.45	13.759%	$72.1801	$72.18	$72.20	$72.20
7 purchase totals =	$584.92		$629.9368	$629.93	$629.95	$629.90