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	$177.52	3.362%	$183.4882	$183.49	$183.50	$183.50
Purchase #2	$104.76	7.124%	$112.2231	$112.22	$112.20	$112.20
Purchase #3	$195.58	7.133%	$209.5307	$209.53	$209.55	$209.50
Purchase #4	$182.30	10.539%	$201.5126	$201.51	$201.50	$201.50
Purchase #5	$113.82	8.572%	$123.5767	$123.58	$123.60	$123.60
Purchase #6	$145.25	13.123%	$164.3112	$164.31	$164.30	$164.30
Purchase #7	$79.70	12.632%	$89.7677	$89.77	$89.75	$89.80
7 purchase totals =	$998.93		$1,084.4102	$1,084.41	$1,084.40	$1,084.40