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	$7.44	5.842%	$7.8746	$7.87	$7.85	$7.90
Purchase #2	$35.43	13.279%	$40.1347	$40.13	$40.15	$40.10
Purchase #3	$69.68	6.765%	$74.3939	$74.39	$74.40	$74.40
Purchase #4	$48.68	11.220%	$54.1419	$54.14	$54.15	$54.10
Purchase #5	$135.57	8.836%	$147.549	$147.55	$147.55	$147.50
Purchase #6	$56.61	4.526%	$59.1722	$59.17	$59.15	$59.20
Purchase #7	$51.28	7.688%	$55.2224	$55.22	$55.20	$55.20
7 purchase totals =	$404.69		$438.4887	$438.47	$438.45	$438.40