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	$70.64	9.858%	$77.6037	$77.60	$77.60	$77.60
Purchase #2	$208.39	10.386%	$230.0334	$230.03	$230.05	$230.00
Purchase #3	$245.56	5.491%	$259.0437	$259.04	$259.05	$259.00
Purchase #4	$111.65	8.200%	$120.8053	$120.81	$120.80	$120.80
Purchase #5	$35.35	8.794%	$38.4587	$38.46	$38.45	$38.50
Purchase #6	$201.89	13.743%	$229.6357	$229.64	$229.65	$229.60
Purchase #7	$82.90	7.754%	$89.3281	$89.33	$89.35	$89.30
7 purchase totals =	$956.38		$1,044.9086	$1,044.91	$1,044.95	$1,044.80