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	$7.86	6.464%	$8.3681	$8.37	$8.35	$8.40
Purchase #2	$63.98	5.328%	$67.3889	$67.39	$67.40	$67.40
Purchase #3	$65.52	11.585%	$73.1105	$73.11	$73.10	$73.10
Purchase #4	$235.70	12.546%	$265.2709	$265.27	$265.25	$265.30
Purchase #5	$191.37	11.150%	$212.7078	$212.71	$212.70	$212.70
Purchase #6	$243.31	5.142%	$255.821	$255.82	$255.80	$255.80
Purchase #7	$192.48	9.640%	$211.0351	$211.04	$211.05	$211.00
7 purchase totals =	$1,000.22		$1,093.7023	$1,093.71	$1,093.65	$1,093.70