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	$246.66	8.745%	$268.2304	$268.23	$268.25	$268.20
Purchase #2	$134.89	12.595%	$151.8794	$151.88	$151.90	$151.90
Purchase #3	$142.72	3.625%	$147.8936	$147.89	$147.90	$147.90
Purchase #4	$119.65	4.361%	$124.8679	$124.87	$124.85	$124.90
Purchase #5	$38.66	8.190%	$41.8263	$41.83	$41.85	$41.80
Purchase #6	$192.34	4.339%	$200.6856	$200.69	$200.70	$200.70
Purchase #7	$161.96	6.109%	$171.8541	$171.85	$171.85	$171.90
7 purchase totals =	$1,036.88		$1,107.2373	$1,107.24	$1,107.30	$1,107.30