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	$150.92	6.179%	$160.2453	$160.25	$160.25	$160.20
Purchase #2	$75.56	3.382%	$78.1154	$78.12	$78.10	$78.10
Purchase #3	$35.32	12.862%	$39.8629	$39.86	$39.85	$39.90
Purchase #4	$99.75	5.245%	$104.9819	$104.98	$105.00	$105.00
Purchase #5	$175.26	8.844%	$190.76	$190.76	$190.75	$190.80
Purchase #6	$142.82	4.343%	$149.0227	$149.02	$149.00	$149.00
Purchase #7	$43.83	3.646%	$45.428	$45.43	$45.45	$45.40
7 purchase totals =	$723.46		$768.4162	$768.42	$768.40	$768.40