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	$89.27	3.551%	$92.44	$92.44	$92.45	$92.40
Purchase #2	$71.56	4.517%	$74.7924	$74.79	$74.80	$74.80
Purchase #3	$33.51	6.720%	$35.7619	$35.76	$35.75	$35.80
Purchase #4	$74.90	10.522%	$82.781	$82.78	$82.80	$82.80
Purchase #5	$160.81	6.687%	$171.5634	$171.56	$171.55	$171.60
Purchase #6	$44.46	11.252%	$49.4626	$49.46	$49.45	$49.50
Purchase #7	$16.40	12.707%	$18.4839	$18.48	$18.50	$18.50
7 purchase totals =	$490.91		$525.2852	$525.27	$525.30	$525.40