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	$103.49	8.233%	$112.0103	$112.01	$112.00	$112.00
Purchase #2	$206.33	13.608%	$234.4074	$234.41	$234.40	$234.40
Purchase #3	$129.93	11.201%	$144.4835	$144.48	$144.50	$144.50
Purchase #4	$85.76	4.789%	$89.867	$89.87	$89.85	$89.90
Purchase #5	$98.89	10.808%	$109.578	$109.58	$109.60	$109.60
Purchase #6	$126.27	8.148%	$136.5585	$136.56	$136.55	$136.60
Purchase #7	$191.35	10.669%	$211.7651	$211.77	$211.75	$211.80
7 purchase totals =	$942.02		$1,038.6698	$1,038.68	$1,038.65	$1,038.80