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	$98.30	4.708%	$102.928	$102.93	$102.95	$102.90
Purchase #2	$75.90	13.732%	$86.3226	$86.32	$86.30	$86.30
Purchase #3	$45.51	5.813%	$48.1555	$48.16	$48.15	$48.20
Purchase #4	$184.67	3.718%	$191.536	$191.54	$191.55	$191.50
Purchase #5	$80.88	10.665%	$89.5059	$89.51	$89.50	$89.50
Purchase #6	$169.92	10.634%	$187.9893	$187.99	$188.00	$188.00
Purchase #7	$41.69	4.117%	$43.4064	$43.41	$43.40	$43.40
7 purchase totals =	$696.87		$749.8437	$749.86	$749.85	$749.80