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	$118.74	10.231%	$130.8883	$130.89	$130.90	$130.90
Purchase #2	$88.88	7.199%	$95.2785	$95.28	$95.30	$95.30
Purchase #3	$198.89	10.144%	$219.0654	$219.07	$219.05	$219.10
Purchase #4	$113.63	5.109%	$119.4354	$119.44	$119.45	$119.40
Purchase #5	$125.33	4.791%	$131.3346	$131.33	$131.35	$131.30
Purchase #6	$89.74	4.150%	$93.4642	$93.46	$93.45	$93.50
Purchase #7	$200.32	8.438%	$217.223	$217.22	$217.20	$217.20
7 purchase totals =	$935.53		$1,006.6894	$1,006.69	$1,006.70	$1,006.70