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	$12.88	9.753%	$14.1362	$14.14	$14.15	$14.10
Purchase #2	$140.99	13.871%	$160.5467	$160.55	$160.55	$160.50
Purchase #3	$94.37	11.711%	$105.4217	$105.42	$105.40	$105.40
Purchase #4	$229.91	8.459%	$249.3581	$249.36	$249.35	$249.40
Purchase #5	$25.30	10.664%	$27.998	$28.00	$28.00	$28.00
Purchase #6	$109.87	12.609%	$123.7235	$123.72	$123.70	$123.70
Purchase #7	$109.45	12.650%	$123.2954	$123.30	$123.30	$123.30
7 purchase totals =	$722.77		$804.4796	$804.49	$804.45	$804.40