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	$214.90	12.786%	$242.3771	$242.38	$242.40	$242.40
Purchase #2	$94.41	5.657%	$99.7508	$99.75	$99.75	$99.80
Purchase #3	$105.85	11.620%	$118.1498	$118.15	$118.15	$118.10
Purchase #4	$96.66	9.138%	$105.4928	$105.49	$105.50	$105.50
Purchase #5	$165.55	12.377%	$186.0401	$186.04	$186.05	$186.00
Purchase #6	$170.44	6.481%	$181.4862	$181.49	$181.50	$181.50
Purchase #7	$131.48	9.634%	$144.1468	$144.15	$144.15	$144.10
7 purchase totals =	$979.29		$1,077.4436	$1,077.45	$1,077.50	$1,077.40