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	$200.31	13.182%	$226.7149	$226.71	$226.70	$226.70
Purchase #2	$53.80	4.582%	$56.2651	$56.27	$56.25	$56.30
Purchase #3	$121.89	4.782%	$127.7188	$127.72	$127.70	$127.70
Purchase #4	$98.38	4.561%	$102.8671	$102.87	$102.85	$102.90
Purchase #5	$86.86	8.699%	$94.416	$94.42	$94.40	$94.40
Purchase #6	$105.49	3.745%	$109.4406	$109.44	$109.45	$109.40
Purchase #7	$243.57	3.389%	$251.8246	$251.82	$251.80	$251.80
7 purchase totals =	$910.30		$969.2471	$969.25	$969.15	$969.20