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	$84.70	8.334%	$91.7589	$91.76	$91.75	$91.80
Purchase #2	$127.65	13.124%	$144.4028	$144.40	$144.40	$144.40
Purchase #3	$140.38	5.280%	$147.7921	$147.79	$147.80	$147.80
Purchase #4	$105.88	6.155%	$112.3969	$112.40	$112.40	$112.40
Purchase #5	$78.38	6.654%	$83.5954	$83.60	$83.60	$83.60
Purchase #6	$197.44	7.195%	$211.6458	$211.65	$211.65	$211.60
Purchase #7	$220.59	4.580%	$230.693	$230.69	$230.70	$230.70
7 purchase totals =	$955.02		$1,022.2849	$1,022.29	$1,022.30	$1,022.30