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	$11.35	11.106%	$12.6105	$12.61	$12.60	$12.60
Purchase #2	$117.83	4.351%	$122.9568	$122.96	$122.95	$123.00
Purchase #3	$156.98	10.864%	$174.0343	$174.03	$174.05	$174.00
Purchase #4	$207.60	7.842%	$223.88	$223.88	$223.90	$223.90
Purchase #5	$50.79	8.413%	$55.063	$55.06	$55.05	$55.10
Purchase #6	$70.27	12.165%	$78.8183	$78.82	$78.80	$78.80
Purchase #7	$45.73	4.782%	$47.9168	$47.92	$47.90	$47.90
7 purchase totals =	$660.55		$715.2797	$715.28	$715.25	$715.30