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	$43.87	5.822%	$46.4241	$46.42	$46.40	$46.40
Purchase #2	$109.61	11.416%	$122.1231	$122.12	$122.10	$122.10
Purchase #3	$121.49	5.224%	$127.8366	$127.84	$127.85	$127.80
Purchase #4	$89.46	10.851%	$99.1673	$99.17	$99.15	$99.20
Purchase #5	$136.36	6.254%	$144.888	$144.89	$144.90	$144.90
Purchase #6	$167.29	11.745%	$186.9382	$186.94	$186.95	$186.90
Purchase #7	$79.55	8.790%	$86.5424	$86.54	$86.55	$86.50
7 purchase totals =	$747.63		$813.9197	$813.92	$813.90	$813.80