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	$84.92	13.260%	$96.1804	$96.18	$96.20	$96.20
Purchase #2	$103.72	11.106%	$115.2391	$115.24	$115.25	$115.20
Purchase #3	$90.79	9.865%	$99.7464	$99.75	$99.75	$99.70
Purchase #4	$69.66	12.842%	$78.6057	$78.61	$78.60	$78.60
Purchase #5	$250.35	10.395%	$276.3739	$276.37	$276.35	$276.40
Purchase #6	$143.70	11.307%	$159.9482	$159.95	$159.95	$159.90
Purchase #7	$190.76	12.817%	$215.2097	$215.21	$215.20	$215.20
7 purchase totals =	$933.90		$1,041.3034	$1,041.31	$1,041.30	$1,041.20