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	$239.28	4.214%	$249.3633	$249.36	$249.35	$249.40
Purchase #2	$107.36	3.546%	$111.167	$111.17	$111.15	$111.20
Purchase #3	$116.88	12.608%	$131.6162	$131.62	$131.60	$131.60
Purchase #4	$16.86	10.713%	$18.6662	$18.67	$18.65	$18.70
Purchase #5	$210.52	9.194%	$229.8752	$229.88	$229.90	$229.90
Purchase #6	$209.32	3.216%	$216.0517	$216.05	$216.05	$216.10
Purchase #7	$67.41	7.201%	$72.2642	$72.26	$72.25	$72.30
7 purchase totals =	$967.63		$1,029.0038	$1,029.01	$1,028.95	$1,029.20