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	$88.94	8.536%	$96.5319	$96.53	$96.55	$96.50
Purchase #2	$244.59	9.608%	$268.0902	$268.09	$268.10	$268.10
Purchase #3	$7.55	4.561%	$7.8944	$7.89	$7.90	$7.90
Purchase #4	$173.49	11.739%	$193.856	$193.86	$193.85	$193.90
Purchase #5	$120.64	5.344%	$127.087	$127.09	$127.10	$127.10
Purchase #6	$243.45	4.770%	$255.0626	$255.06	$255.05	$255.10
Purchase #7	$51.43	13.462%	$58.3535	$58.35	$58.35	$58.40
7 purchase totals =	$930.09		$1,006.8756	$1,006.87	$1,006.90	$1,007.00