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	$238.73	11.537%	$266.2723	$266.27	$266.25	$266.30
Purchase #2	$60.92	10.140%	$67.0973	$67.10	$67.10	$67.10
Purchase #3	$124.69	12.187%	$139.886	$139.89	$139.90	$139.90
Purchase #4	$125.36	13.409%	$142.1695	$142.17	$142.15	$142.20
Purchase #5	$215.61	6.464%	$229.547	$229.55	$229.55	$229.50
Purchase #6	$115.43	13.606%	$131.1354	$131.14	$131.15	$131.10
Purchase #7	$71.49	4.133%	$74.4447	$74.44	$74.45	$74.40
7 purchase totals =	$952.23		$1,050.5522	$1,050.56	$1,050.55	$1,050.50