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	$104.71	8.460%	$113.5685	$113.57	$113.55	$113.60
Purchase #2	$190.27	11.371%	$211.9056	$211.91	$211.90	$211.90
Purchase #3	$203.61	7.823%	$219.5384	$219.54	$219.55	$219.50
Purchase #4	$91.43	4.314%	$95.3743	$95.37	$95.35	$95.40
Purchase #5	$99.86	11.742%	$111.5856	$111.59	$111.60	$111.60
Purchase #6	$162.54	8.443%	$176.2633	$176.26	$176.25	$176.30
Purchase #7	$96.42	4.611%	$100.8659	$100.87	$100.85	$100.90
7 purchase totals =	$948.84		$1,029.1016	$1,029.11	$1,029.05	$1,029.20