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	$200.63	5.420%	$211.5041	$211.50	$211.50	$211.50
Purchase #2	$153.96	3.667%	$159.6057	$159.61	$159.60	$159.60
Purchase #3	$167.64	8.334%	$181.6111	$181.61	$181.60	$181.60
Purchase #4	$167.86	7.773%	$180.9078	$180.91	$180.90	$180.90
Purchase #5	$37.76	4.415%	$39.4271	$39.43	$39.45	$39.40
Purchase #6	$136.87	8.129%	$147.9962	$148.00	$148.00	$148.00
Purchase #7	$119.28	7.139%	$127.7954	$127.80	$127.80	$127.80
7 purchase totals =	$984.00		$1,048.8474	$1,048.86	$1,048.85	$1,048.80