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	$200.94	11.181%	$223.4071	$223.41	$223.40	$223.40
Purchase #2	$120.78	6.107%	$128.156	$128.16	$128.15	$128.20
Purchase #3	$54.39	8.535%	$59.0322	$59.03	$59.05	$59.00
Purchase #4	$28.29	11.620%	$31.5773	$31.58	$31.60	$31.60
Purchase #5	$108.77	6.757%	$116.1196	$116.12	$116.10	$116.10
Purchase #6	$117.76	8.213%	$127.4316	$127.43	$127.45	$127.40
Purchase #7	$79.30	9.291%	$86.6678	$86.67	$86.65	$86.70
7 purchase totals =	$710.23		$772.3916	$772.40	$772.40	$772.40