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	$102.30	4.328%	$106.7275	$106.73	$106.75	$106.70
Purchase #2	$93.54	9.454%	$102.3833	$102.38	$102.40	$102.40
Purchase #3	$16.91	8.245%	$18.3042	$18.30	$18.30	$18.30
Purchase #4	$64.88	8.155%	$70.171	$70.17	$70.15	$70.20
Purchase #5	$38.80	12.709%	$43.7311	$43.73	$43.75	$43.70
Purchase #6	$48.45	12.614%	$54.5615	$54.56	$54.55	$54.60
Purchase #7	$133.44	13.579%	$151.5598	$151.56	$151.55	$151.60
7 purchase totals =	$498.32		$547.4384	$547.43	$547.45	$547.50