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	$145.33	6.298%	$154.4829	$154.48	$154.50	$154.50
Purchase #2	$115.37	10.402%	$127.3708	$127.37	$127.35	$127.40
Purchase #3	$207.75	11.641%	$231.9342	$231.93	$231.95	$231.90
Purchase #4	$11.28	6.355%	$11.9968	$12.00	$12.00	$12.00
Purchase #5	$199.46	11.855%	$223.106	$223.11	$223.10	$223.10
Purchase #6	$65.55	12.487%	$73.7352	$73.74	$73.75	$73.70
Purchase #7	$224.36	6.410%	$238.7415	$238.74	$238.75	$238.70
7 purchase totals =	$969.10		$1,061.3674	$1,061.37	$1,061.40	$1,061.30