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	$109.83	8.830%	$119.528	$119.53	$119.55	$119.50
Purchase #2	$174.56	5.568%	$184.2795	$184.28	$184.30	$184.30
Purchase #3	$91.46	5.631%	$96.6101	$96.61	$96.60	$96.60
Purchase #4	$122.99	6.855%	$131.421	$131.42	$131.40	$131.40
Purchase #5	$93.88	7.418%	$100.844	$100.84	$100.85	$100.80
Purchase #6	$87.48	8.446%	$94.8686	$94.87	$94.85	$94.90
Purchase #7	$180.66	13.608%	$205.2442	$205.24	$205.25	$205.20
7 purchase totals =	$860.86		$932.7954	$932.79	$932.80	$932.70