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	$48.34	12.518%	$54.3912	$54.39	$54.40	$54.40
Purchase #2	$52.76	12.483%	$59.346	$59.35	$59.35	$59.30
Purchase #3	$109.68	5.814%	$116.0568	$116.06	$116.05	$116.10
Purchase #4	$166.83	4.318%	$174.0337	$174.03	$174.05	$174.00
Purchase #5	$131.92	9.727%	$144.7519	$144.75	$144.75	$144.80
Purchase #6	$24.26	5.414%	$25.5734	$25.57	$25.55	$25.60
Purchase #7	$117.88	13.147%	$133.3777	$133.38	$133.40	$133.40
7 purchase totals =	$651.67		$707.5307	$707.53	$707.55	$707.60