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	$139.37	4.109%	$145.0967	$145.10	$145.10	$145.10
Purchase #2	$42.98	5.472%	$45.3319	$45.33	$45.35	$45.30
Purchase #3	$134.34	11.715%	$150.0779	$150.08	$150.10	$150.10
Purchase #4	$10.44	5.132%	$10.9758	$10.98	$11.00	$11.00
Purchase #5	$170.98	7.859%	$184.4173	$184.42	$184.40	$184.40
Purchase #6	$242.85	12.664%	$273.6045	$273.60	$273.60	$273.60
Purchase #7	$59.90	8.540%	$65.0155	$65.02	$65.00	$65.00
7 purchase totals =	$800.86		$874.5196	$874.53	$874.55	$874.50