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	$223.89	7.693%	$241.1139	$241.11	$241.10	$241.10
Purchase #2	$118.87	6.552%	$126.6584	$126.66	$126.65	$126.70
Purchase #3	$98.29	7.722%	$105.88	$105.88	$105.90	$105.90
Purchase #4	$153.36	4.559%	$160.3517	$160.35	$160.35	$160.40
Purchase #5	$50.79	12.465%	$57.121	$57.12	$57.10	$57.10
Purchase #6	$128.59	9.591%	$140.9231	$140.92	$140.90	$140.90
Purchase #7	$245.88	13.550%	$279.1967	$279.20	$279.20	$279.20
7 purchase totals =	$1,019.67		$1,111.2448	$1,111.24	$1,111.20	$1,111.30