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	$198.84	4.823%	$208.4301	$208.43	$208.45	$208.40
Purchase #2	$216.56	12.215%	$243.0128	$243.01	$243.00	$243.00
Purchase #3	$53.85	11.252%	$59.9092	$59.91	$59.90	$59.90
Purchase #4	$200.27	10.369%	$221.036	$221.04	$221.05	$221.00
Purchase #5	$186.96	12.532%	$210.3898	$210.39	$210.40	$210.40
Purchase #6	$46.58	9.709%	$51.1025	$51.10	$51.10	$51.10
Purchase #7	$129.79	9.826%	$142.5432	$142.54	$142.55	$142.50
7 purchase totals =	$1,032.85		$1,136.4236	$1,136.42	$1,136.45	$1,136.30