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	$133.63	7.269%	$143.3436	$143.34	$143.35	$143.30
Purchase #2	$39.87	12.813%	$44.9785	$44.98	$45.00	$45.00
Purchase #3	$53.92	7.357%	$57.8869	$57.89	$57.90	$57.90
Purchase #4	$227.61	4.862%	$238.6764	$238.68	$238.70	$238.70
Purchase #5	$172.54	6.367%	$183.5256	$183.53	$183.55	$183.50
Purchase #6	$77.70	7.498%	$83.5259	$83.53	$83.55	$83.50
Purchase #7	$95.89	6.427%	$102.0529	$102.05	$102.05	$102.10
7 purchase totals =	$801.16		$853.9898	$854.00	$854.10	$854.00