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	$168.31	5.776%	$178.0316	$178.03	$178.05	$178.00
Purchase #2	$28.27	10.220%	$31.1592	$31.16	$31.15	$31.20
Purchase #3	$44.91	3.476%	$46.4711	$46.47	$46.45	$46.50
Purchase #4	$194.93	12.490%	$219.2768	$219.28	$219.30	$219.30
Purchase #5	$31.44	4.490%	$32.8517	$32.85	$32.85	$32.90
Purchase #6	$23.85	13.782%	$27.137	$27.14	$27.15	$27.10
Purchase #7	$30.78	6.797%	$32.8721	$32.87	$32.85	$32.90
7 purchase totals =	$522.49		$567.7995	$567.80	$567.80	$567.90