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	$32.63	4.818%	$34.2021	$34.20	$34.20	$34.20
Purchase #2	$136.74	6.341%	$145.4107	$145.41	$145.40	$145.40
Purchase #3	$59.45	13.686%	$67.5863	$67.59	$67.60	$67.60
Purchase #4	$186.31	5.251%	$196.0931	$196.09	$196.10	$196.10
Purchase #5	$84.88	7.716%	$91.4293	$91.43	$91.45	$91.40
Purchase #6	$26.72	7.848%	$28.817	$28.82	$28.80	$28.80
Purchase #7	$128.80	10.848%	$142.7722	$142.77	$142.75	$142.80
7 purchase totals =	$655.53		$706.3107	$706.31	$706.30	$706.30