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	$116.41	13.321%	$131.917	$131.92	$131.90	$131.90
Purchase #2	$249.29	5.666%	$263.4148	$263.41	$263.40	$263.40
Purchase #3	$103.94	5.130%	$109.2721	$109.27	$109.25	$109.30
Purchase #4	$93.34	10.254%	$102.9111	$102.91	$102.90	$102.90
Purchase #5	$30.28	9.302%	$33.0966	$33.10	$33.10	$33.10
Purchase #6	$187.79	6.476%	$199.9513	$199.95	$199.95	$200.00
Purchase #7	$189.74	12.454%	$213.3702	$213.37	$213.35	$213.40
7 purchase totals =	$970.79		$1,053.9331	$1,053.93	$1,053.85	$1,054.00