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	$93.67	10.129%	$103.1578	$103.16	$103.15	$103.20
Purchase #2	$213.88	4.601%	$223.7206	$223.72	$223.70	$223.70
Purchase #3	$183.65	11.764%	$205.2546	$205.25	$205.25	$205.30
Purchase #4	$57.41	6.524%	$61.1554	$61.16	$61.15	$61.20
Purchase #5	$42.69	10.649%	$47.2361	$47.24	$47.25	$47.20
Purchase #6	$51.35	6.535%	$54.7057	$54.71	$54.70	$54.70
Purchase #7	$6.60	12.824%	$7.4464	$7.45	$7.45	$7.40
7 purchase totals =	$649.25		$702.6766	$702.69	$702.65	$702.70