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	$145.69	11.807%	$162.8916	$162.89	$162.90	$162.90
Purchase #2	$34.63	7.737%	$37.3093	$37.31	$37.30	$37.30
Purchase #3	$138.91	10.418%	$153.3816	$153.38	$153.40	$153.40
Purchase #4	$89.66	9.751%	$98.4027	$98.40	$98.40	$98.40
Purchase #5	$230.26	12.218%	$258.3932	$258.39	$258.40	$258.40
Purchase #6	$244.48	10.860%	$271.0305	$271.03	$271.05	$271.00
Purchase #7	$154.75	12.519%	$174.1232	$174.12	$174.10	$174.10
7 purchase totals =	$1,038.38		$1,155.5321	$1,155.52	$1,155.55	$1,155.50