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	$111.52	6.131%	$118.3573	$118.36	$118.35	$118.40
Purchase #2	$52.38	7.532%	$56.3253	$56.33	$56.35	$56.30
Purchase #3	$231.27	13.745%	$263.0581	$263.06	$263.05	$263.10
Purchase #4	$96.56	5.640%	$102.006	$102.01	$102.00	$102.00
Purchase #5	$40.50	5.535%	$42.7417	$42.74	$42.75	$42.70
Purchase #6	$176.93	11.792%	$197.7936	$197.79	$197.80	$197.80
Purchase #7	$240.53	10.564%	$265.9396	$265.94	$265.95	$265.90
7 purchase totals =	$949.69		$1,046.2216	$1,046.23	$1,046.25	$1,046.20