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	$137.25	11.374%	$152.8608	$152.86	$152.85	$152.90
Purchase #2	$106.62	6.696%	$113.7593	$113.76	$113.75	$113.80
Purchase #3	$94.49	10.232%	$104.1582	$104.16	$104.15	$104.20
Purchase #4	$98.74	10.656%	$109.2617	$109.26	$109.25	$109.30
Purchase #5	$146.90	4.798%	$153.9483	$153.95	$153.95	$153.90
Purchase #6	$176.94	6.714%	$188.8198	$188.82	$188.80	$188.80
Purchase #7	$105.84	5.228%	$111.3733	$111.37	$111.35	$111.40
7 purchase totals =	$866.78		$934.1814	$934.18	$934.10	$934.30