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	$115.93	10.632%	$128.2557	$128.26	$128.25	$128.30
Purchase #2	$216.83	10.119%	$238.771	$238.77	$238.75	$238.80
Purchase #3	$146.73	12.787%	$165.4924	$165.49	$165.50	$165.50
Purchase #4	$142.57	7.523%	$153.2955	$153.30	$153.30	$153.30
Purchase #5	$41.70	3.202%	$43.0352	$43.04	$43.05	$43.00
Purchase #6	$145.76	6.559%	$155.3204	$155.32	$155.30	$155.30
Purchase #7	$207.95	9.266%	$227.2186	$227.22	$227.20	$227.20
7 purchase totals =	$1,017.47		$1,111.3888	$1,111.40	$1,111.35	$1,111.40