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	$150.47	6.752%	$160.6297	$160.63	$160.65	$160.60
Purchase #2	$92.92	12.341%	$104.3873	$104.39	$104.40	$104.40
Purchase #3	$85.29	7.348%	$91.5571	$91.56	$91.55	$91.60
Purchase #4	$215.25	7.545%	$231.4906	$231.49	$231.50	$231.50
Purchase #5	$147.80	3.543%	$153.0366	$153.04	$153.05	$153.00
Purchase #6	$156.26	5.821%	$165.3559	$165.36	$165.35	$165.40
Purchase #7	$171.70	4.874%	$180.0687	$180.07	$180.05	$180.10
7 purchase totals =	$1,019.69		$1,086.5259	$1,086.54	$1,086.55	$1,086.60