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	$98.41	12.772%	$110.9789	$110.98	$111.00	$111.00
Purchase #2	$89.89	13.303%	$101.8481	$101.85	$101.85	$101.80
Purchase #3	$165.85	10.798%	$183.7585	$183.76	$183.75	$183.80
Purchase #4	$158.77	6.304%	$168.7789	$168.78	$168.80	$168.80
Purchase #5	$175.33	10.602%	$193.9185	$193.92	$193.90	$193.90
Purchase #6	$67.55	13.295%	$76.5308	$76.53	$76.55	$76.50
Purchase #7	$176.89	4.172%	$184.2699	$184.27	$184.25	$184.30
7 purchase totals =	$932.69		$1,020.0836	$1,020.09	$1,020.10	$1,020.10