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	$181.85	3.179%	$187.631	$187.63	$187.65	$187.60
Purchase #2	$249.85	7.515%	$268.6262	$268.63	$268.65	$268.60
Purchase #3	$63.85	12.124%	$71.5912	$71.59	$71.60	$71.60
Purchase #4	$67.60	7.549%	$72.7031	$72.70	$72.70	$72.70
Purchase #5	$145.98	3.779%	$151.4966	$151.50	$151.50	$151.50
Purchase #6	$167.88	10.641%	$185.7441	$185.74	$185.75	$185.70
Purchase #7	$249.87	13.774%	$284.2871	$284.29	$284.30	$284.30
7 purchase totals =	$1,126.88		$1,222.0793	$1,222.08	$1,222.15	$1,222.00