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	$149.30	6.801%	$159.4539	$159.45	$159.45	$159.50
Purchase #2	$248.44	7.439%	$266.9215	$266.92	$266.90	$266.90
Purchase #3	$95.84	3.820%	$99.5011	$99.50	$99.50	$99.50
Purchase #4	$179.35	11.234%	$199.4982	$199.50	$199.50	$199.50
Purchase #5	$104.64	6.637%	$111.585	$111.59	$111.60	$111.60
Purchase #6	$215.76	3.428%	$223.1563	$223.16	$223.15	$223.20
Purchase #7	$141.60	4.587%	$148.0952	$148.10	$148.10	$148.10
7 purchase totals =	$1,134.93		$1,208.2112	$1,208.22	$1,208.20	$1,208.30