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	$223.64	9.523%	$244.9372	$244.94	$244.95	$244.90
Purchase #2	$93.57	12.565%	$105.3271	$105.33	$105.35	$105.30
Purchase #3	$27.99	13.365%	$31.7309	$31.73	$31.75	$31.70
Purchase #4	$86.29	4.343%	$90.0376	$90.04	$90.05	$90.00
Purchase #5	$191.49	8.483%	$207.7341	$207.73	$207.75	$207.70
Purchase #6	$167.58	10.807%	$185.6904	$185.69	$185.70	$185.70
Purchase #7	$159.71	13.341%	$181.0169	$181.02	$181.00	$181.00
7 purchase totals =	$950.27		$1,046.4742	$1,046.48	$1,046.55	$1,046.30