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	$223.70	8.189%	$242.0188	$242.02	$242.00	$242.00
Purchase #2	$206.25	7.643%	$222.0137	$222.01	$222.00	$222.00
Purchase #3	$223.37	11.529%	$249.1223	$249.12	$249.10	$249.10
Purchase #4	$74.27	8.630%	$80.6795	$80.68	$80.70	$80.70
Purchase #5	$104.42	7.701%	$112.4614	$112.46	$112.45	$112.50
Purchase #6	$51.56	11.640%	$57.5616	$57.56	$57.55	$57.60
Purchase #7	$173.88	12.814%	$196.161	$196.16	$196.15	$196.20
7 purchase totals =	$1,057.45		$1,160.0183	$1,160.01	$1,159.95	$1,160.10