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	$110.59	4.710%	$115.7988	$115.80	$115.80	$115.80
Purchase #2	$88.71	13.338%	$100.5421	$100.54	$100.55	$100.50
Purchase #3	$90.65	5.461%	$95.6004	$95.60	$95.60	$95.60
Purchase #4	$191.42	4.579%	$200.1851	$200.19	$200.20	$200.20
Purchase #5	$123.50	6.475%	$131.4966	$131.50	$131.50	$131.50
Purchase #6	$172.76	4.454%	$180.4547	$180.45	$180.45	$180.50
Purchase #7	$229.63	8.266%	$248.6112	$248.61	$248.60	$248.60
7 purchase totals =	$1,007.26		$1,072.6889	$1,072.69	$1,072.70	$1,072.70