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	$185.66	5.664%	$196.1758	$196.18	$196.20	$196.20
Purchase #2	$51.27	4.620%	$53.6387	$53.64	$53.65	$53.60
Purchase #3	$156.81	7.664%	$168.8279	$168.83	$168.85	$168.80
Purchase #4	$231.56	9.419%	$253.3706	$253.37	$253.35	$253.40
Purchase #5	$54.86	11.278%	$61.0471	$61.05	$61.05	$61.00
Purchase #6	$148.75	3.604%	$154.111	$154.11	$154.10	$154.10
Purchase #7	$22.46	12.259%	$25.2134	$25.21	$25.20	$25.20
7 purchase totals =	$851.37		$912.3845	$912.39	$912.40	$912.30