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	$184.65	8.743%	$200.7939	$200.79	$200.80	$200.80
Purchase #2	$203.30	4.190%	$211.8183	$211.82	$211.80	$211.80
Purchase #3	$95.86	3.412%	$99.1307	$99.13	$99.15	$99.10
Purchase #4	$134.93	7.191%	$144.6328	$144.63	$144.65	$144.60
Purchase #5	$99.50	4.120%	$103.5994	$103.60	$103.60	$103.60
Purchase #6	$124.28	7.451%	$133.5401	$133.54	$133.55	$133.50
Purchase #7	$100.90	8.567%	$109.5441	$109.54	$109.55	$109.50
7 purchase totals =	$943.42		$1,003.0593	$1,003.05	$1,003.10	$1,002.90