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	$101.50	10.595%	$112.2539	$112.25	$112.25	$112.30
Purchase #2	$59.90	4.681%	$62.7039	$62.70	$62.70	$62.70
Purchase #3	$73.28	13.477%	$83.1559	$83.16	$83.15	$83.20
Purchase #4	$110.56	9.326%	$120.8708	$120.87	$120.85	$120.90
Purchase #5	$175.93	11.798%	$196.6862	$196.69	$196.70	$196.70
Purchase #6	$232.69	6.676%	$248.2244	$248.22	$248.20	$248.20
Purchase #7	$59.60	6.147%	$63.2636	$63.26	$63.25	$63.30
7 purchase totals =	$813.46		$887.1587	$887.15	$887.10	$887.30