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	$219.53	9.768%	$240.9737	$240.97	$240.95	$241.00
Purchase #2	$64.27	5.670%	$67.9141	$67.91	$67.90	$67.90
Purchase #3	$26.46	5.590%	$27.9391	$27.94	$27.95	$27.90
Purchase #4	$124.51	11.759%	$139.1511	$139.15	$139.15	$139.20
Purchase #5	$6.84	8.334%	$7.41	$7.41	$7.40	$7.40
Purchase #6	$106.52	4.569%	$111.3869	$111.39	$111.40	$111.40
Purchase #7	$76.83	9.408%	$84.0582	$84.06	$84.05	$84.10
7 purchase totals =	$624.96		$678.8331	$678.83	$678.80	$678.90