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	$178.30	6.722%	$190.2853	$190.29	$190.30	$190.30
Purchase #2	$139.58	6.118%	$148.1195	$148.12	$148.10	$148.10
Purchase #3	$63.59	13.801%	$72.3661	$72.37	$72.35	$72.40
Purchase #4	$80.90	11.225%	$89.981	$89.98	$90.00	$90.00
Purchase #5	$184.79	7.360%	$198.3905	$198.39	$198.40	$198.40
Purchase #6	$43.76	5.515%	$46.1734	$46.17	$46.15	$46.20
Purchase #7	$184.33	7.528%	$198.2064	$198.21	$198.20	$198.20
7 purchase totals =	$875.25		$943.5222	$943.53	$943.50	$943.60