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	$114.95	13.708%	$130.7073	$130.71	$130.70	$130.70
Purchase #2	$59.36	13.463%	$67.3516	$67.35	$67.35	$67.40
Purchase #3	$61.60	5.566%	$65.0287	$65.03	$65.05	$65.00
Purchase #4	$116.38	9.295%	$127.1975	$127.20	$127.20	$127.20
Purchase #5	$179.74	5.792%	$190.1505	$190.15	$190.15	$190.20
Purchase #6	$165.90	11.699%	$185.3086	$185.31	$185.30	$185.30
Purchase #7	$90.63	8.368%	$98.2139	$98.21	$98.20	$98.20
7 purchase totals =	$788.56		$863.9581	$863.96	$863.95	$864.00