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	$99.99	11.447%	$111.4359	$111.44	$111.45	$111.40
Purchase #2	$196.65	7.161%	$210.7321	$210.73	$210.75	$210.70
Purchase #3	$42.82	12.366%	$48.1151	$48.12	$48.10	$48.10
Purchase #4	$112.42	10.399%	$124.1106	$124.11	$124.10	$124.10
Purchase #5	$211.87	10.199%	$233.4786	$233.48	$233.50	$233.50
Purchase #6	$168.70	4.331%	$176.0064	$176.01	$176.00	$176.00
Purchase #7	$93.50	5.868%	$98.9866	$98.99	$99.00	$99.00
7 purchase totals =	$925.95		$1,002.8653	$1,002.88	$1,002.90	$1,002.80